9 Tips to Help Prevent Derm Biopsy Mistakes

Most clinicians do a satisfactory job in choosing when and how to do a skin biopsy, but there is always room for improvement. The nine pointers provided here are based on standard-of-care practices and literature when available and also on the collective experience of the authors, who include a pathologist/dermatologist (JM), dermatopathologist (DZ), primary care physician (BR), and dermatologist/Mohs surgeon (EB).

1. CHOOSE YOUR BIOPSY TYPE WISELY
Using the appropriate type of biopsy can have the greatest effect on a proper diagnosis. The decision of which biopsy type to use is not always easy. The most common biopsy types are shave, punch, excisional, and curettage. Several reference articles detail each type of biopsy commonly used in primary care and how to perform them.^1,2

Each type of biopsy has inherent advantages and disadvantages. In general, the shave biopsy is most commonly used for lesions that are solitary and elevated and give the impression that a sufficient amount of tissue can be sampled with this technique. The punch biopsy is the best choice for most “rashes” (inflammatory skin disorders).² Excisional biopsy is used to remove melanocytic neoplasms or larger lesions. And curettage, while still used by some clinicians for melanocytic lesions because of its speed and simplicity, should almost never be used for diagnostic purposes.

Each technique is described in greater detail in the tips that follow.

Continue for tip #2 >>

 

2. WHEN PERFORMING A SHAVE BIOPSY, AVOID OBTAINING A SAMPLE THAT'S TOO SUPERFICIAL
The advantage of the shave biopsy is that it is minimally invasive and quick to perform. If kept small without compromising the amount of sample retrieved, the scars left by shave biopsies have the potential to blend well. The major disadvantage associated with the shave biopsy is that occasionally, if the shave is not deep enough, an insufficient amount of tissue is obtained. This can make it challenging to establish an accurate diagnosis.

Balancing the need to obtain adequate tissue with the desire to minimize scarring takes skill and experience. Taking a biopsy that is inadequate is a common occurrence. At times, the clinician’s clinical impression may be that a biopsy has obtained adequate tissue, when histologically only the superficial part of the skin surface has been sampled. This often is because of thickening of the superficial skin, whether as a manifestation of the anatomic site (eg, acral skin) or the disease process itself.

Unfortunately, this superficial skin often is nondiagnostic when unaccompanied by underlying epidermis and dermis. It is important to keep this in mind when you are obtaining a skin biopsy, especially when dealing with lesions that are very scaly or keratinized.

An equivocal biopsy wastes time, energy, and money, and it can negatively impact patient care.³ It can be difficult to balance practical aspects of the biopsy (ie, optimizing cosmetic outcomes, minimizing scarring and wound size) with the need to obtain sufficient tissue sampling (see Figure 1).

3. CHOOSE PUNCH OVER SHAVE BIOPSY FOR RASHES
In a punch biopsy, a disposable metal cylinder with a sharpened edge is used to “punch” out a piece of skin that can be examined under the microscope. Punch biopsy is the preferred technique for almost all inflammatory skin conditions (rashes) because the pathologist is able to examine both the superficial and deep portions of the dermis (see Figure 2).⁴  

Pathologists use the pattern of inflammation, in conjunction with epidermal changes, to distinguish different types of inflammatory processes. For example, lichen planus is typically associated with superficial inflammation, while lupus is known to have prominent superficial and deep inflammation.

An inadequate punch biopsy sample can hinder histologic assessment of inflammatory skin disorders that involve both the superficial and deep portions of the dermis and can make arriving at a definitive diagnosis more challenging. The diameter of a punch cylinder ranges from 1 to 8 mm. Smaller punch biopsies often create diagnostic challenges because they provide so little sample. A punch biopsy size of 4 mm is commonly used for rashes.

An advantage of the punch biopsy is that patients are left with linear scars rather than the round, potentially dyspigmented (darker or lighter) scars that are often associated with shave biopsy. A well-sutured punch biopsy can be cosmetically elegant, particularly if closure is oriented along relaxed skin tension lines. For this reason, punch biopsies are well suited for cosmetically sensitive locations (eg, the face), although shave biopsies are also often performed on the face.

Next page: Tip #4 >>

 

4. CHOOSE AN EXCISIONAL BIOPSY FOR A MELANOCYTIC NEOPLASM, WHEN POSSIBLE
The purpose of an excisional biopsy (which typically includes a 1- to 3-mm rim of normal skin around the lesion) is to completely remove a lesion. Excisional biopsy generally is the preferred technique for clinically atypical melanocytic neoplasms (ie, lesions that are not definitively benign).^4-8

When suspicion for melanoma is high, excisional biopsies should be performed with minimal undermining to preserve the accuracy of any future sentinel lymph node biopsy surgeries. Excisional biopsy is the most involved type of biopsy and has the largest potential for cosmetic disfigurement if not properly planned and performed. While guidelines from the American Academy of Dermatology state that “narrow excisional biopsy that encompasses [the] entire breadth of lesion with clinically negative margins to ensure that the lesion is not transected” is preferred, they also acknowledge that partial sampling (incisional biopsy) is acceptable in select clinical circumstances,⁹ such as when a lesion is large or on a cosmetically sensitive site (eg, the face).¹⁰

While a larger punch biopsy (6 or 8 mm) or even deep shave/saucerization may function as an excisional biopsy for very small lesions, this approach can be problematic. For one thing, these techniques are more likely than an excisional biopsy to leave a portion of the lesion in situ. Another concern is that a shave biopsy of a melanocytic lesion can lead to error or difficulty in obtaining the correct diagnosis on later biopsy.¹¹ For pathologists, small or incomplete samples make it challenging to establish an accurate diagnosis.¹² Among melanomas seen at a tertiary referral center, histopathologic misdiagnosis was more common with a punch or shave biopsy than with an excisional biopsy.⁹

It has been shown that partial biopsy for melanoma results in more residual disease at wide local excision and makes it more challenging to properly stage the lesion.^13,14 If a shave biopsy is used to sample a suspected melanocytic neoplasm, it is imperative to document the specific site of the biopsy, indicate the size of the melanocytic lesion on the pathology requisition form, and ensure that all (or nearly all) of the clinically evident lesion is sampled. Detailing the location of the lesion in the chart is not only essential in evaluating the present lesion, but it will serve you well in the future. Without knowing the patient’s clinical history, benign nevi that recur after a prior biopsy can be difficult to histologically distinguish from melanoma (see Figure 3). For more on this, see tip #7.

5. BE CAREFUL WITH CURETTAGE
Curettage is a biopsy technique in which a curette—a surgical tool with a scoop, ring, or loop at the tip—is used in a scraping motion to retrieve tissue from the patient. This type of biopsy often produces a fragmented tissue sample. Its continued use reflects the speed and simplicity with which it can be done. However, curettage destroys the architecture of the tissue of the lesion, which can make it difficult to establish a proper diagnosis, and therefore it is best avoided when performing a biopsy of a melanocytic lesion (see Figure 4).

Continue for tip #6 >>

 

6. REMEMBER THE IMPORTANCE OF PROPER FIXATION AND PROCESSING
As obvious as it may sound, it is important to remember to promptly place sampled tissue in an adequate amount of formalin so that the tissue is submersed in it in the container.¹⁵ Failure to do so can result in improper fixation and will make it difficult to render an appropriate diagnosis. Conventionally, a 10:1 formalin-volume-to-tissue-volume ratio is recommended. If the “cold time”—the amount of time a tissue sample is out of formalin—is too long (> a few hours), an appropriate assessment can be impossible.

Appropriate fixation and fixation times are important because molecular testing is being increasingly used to make pathologic diagnoses.¹⁶ Additionally, aggressively manipulating a biopsy sample while extracting it or placing it in formalin can cause “crush” artifact, which can limit interpretability (see Figure 5).

7. PROPERLY PHOTOGRAPH AND DOCUMENT THE BIOPSY LOCATION
When performing a biopsy of a suspicious neoplasm, clinicians often remove all of the lesion’s superficial components, which means that at the patient’s follow-up appointment and subsequent treatments, only a well-healed biopsy site will remain. The biopsy site may be so well healed that it blends seamlessly into the surrounding skin and is nearly impossible for the clinician to identify. This problem is seen most often when patients present for surgical excision or Mohs micrographic surgery.¹⁷

To properly record the site of a biopsy for future dermatologic exams, take pictures of the lesion at the time of biopsy. The photographs should clearly document the lesion in question and should be taken far enough from the site that surrounding lesions and/or other anatomic landmarks are also visible. Biangulation or triangulation (taking a series of two or three measurements, respectively, from the site of the lesion to nearby anatomic landmarks) can be used in conjunction with photographs.

When using measurements, be as specific and accurate as possible with anatomic terms. For example, measuring the distance from the “ear” is not helpful. It would be more helpful to measure the distance from the “tragus” or the “root of the helix.” Without a properly photographed and documented biopsy site, surgical treatment may need to be delayed until the location can be confirmed.

8. GIVE THE PATHOLOGIST A PERTINENT HISTORY
Providing the pathologist with a sufficient history, including the distribution and appearance of the lesion, and how long the patient has had it, can be essential in narrowing the diagnosis or making the differential diagnoses. Things like medication use or new exposures to perfumes, lotions, or plants can be especially helpful and are often overlooked when filling out the pathology requisition form.

When warranted, phone calls are helpful. You might, for example, call the pathologist and give him or her a more detailed physical examination description or additional pertinent history that was discovered after the requisition was filled out. Providing a good history can make the difference between a specific diagnosis and a broad differential.

Tip #9: Next page >>

 

9. KNOW WHEN TO REFER
There is no shame in asking for a second opinion when evaluating a skin lesion, especially with melanocytic neoplasms, where the stakes can be high, or skin eruptions that do not respond to conventional therapy. Remember, many cases are difficult, even for experts, and require a careful balance of clinical and histopathologic judgment.¹⁸

REFERENCES
1. Pickett H. Shave and punch biopsy for skin lesions. Am Fam Physician. 2011;84:995-1002.
2. Alguire PC, Mathes BM. Skin biopsy techniques for the internist. J Gen Intern Med. 1998;13:46-54.
3. Fernandez EM, Helm T, Ioffreda M, et al. The vanishing biopsy: the trend toward smaller specimens. Cutis. 2005;76:335-339.
4. Hieken TJ, Hernández-Irizarry R, Boll JM, et al. Accuracy of diagnostic biopsy for cutaneous melanoma: implications for surgical oncologists. Int J Surg Oncol. 2013;2013:196493.
5. Scolyer RA, Thompson JF, McCarthy SW, et al. Incomplete biopsy of melanocytic lesions can impair the accuracy of pathological diagnosis. Australas J Dermatol. 2006;47:71-75.
6. McCarthy SW, Scolyer RA. Pitfalls and important issues in the pathologic diagnosis of melanocytic tumors. Ochsner J. 2010;10:66-74.
7. Swanson NA, Lee KK, Gorman A, et al. Biopsy techniques. Diagnosis of melanoma. Dermatol Clin. 2002;20:677-680.
8. Chang TT, Somach SC, Wagamon K, et al. The inadequacy of punch-excised melanocytic lesions: sampling through the block for the determination of “margins.” J Am Acad Dermatol. 2009;60: 990-993.
9. Bichakjian CK, Halpern AC, Johnson TM, et al; American Academy of Dermatology. Guidelines of care for the management of primary cutaneous melanoma. American Academy of Dermatology. J Am Acad Dermatol. 2011;65:1032-1047.
10. Pardasani AG, Leshin B, Hallman JR, et al. Fusiform incisional biopsy for pigmented skin lesions. Dermatol Surg. 2000;26:622-624.
11. King R, Hayzen BA, Page RN, et al. Recurrent nevus phenomenon: a clinicopathologic study of 357 cases and histologic comparison with melanoma with regression. Mod Pathol. 2009;22:611-617.
12. Mills JK, White I, Diggs B, et al. Effect of biopsy type on outcomes in the treatment of primary cutaneous melanoma. Am J Surg. 2013;205:585-590.
13. Stell VH, Norton HJ, Smith KS, et al. Method of biopsy and incidence of positive margins in primary melanoma. Ann Surg Oncol. 2007;14:
893-898.
14. Egnatios GL, Dueck AC, Macdonald JB, et al. The impact of biopsy technique on upstaging, residual disease, and outcome in cutaneous melanoma. Am J Surg. 2011;202:771-778.
15. Ackerman AB, Boer A, Bennin B, et al. Histologic Diagnosis of Inflammatory Skin Disease: An Algorithmic Method Based on Pattern Analysis. New York, NY: Ardor Scribendi; 2005.
16. Hewitt SM, Lewis FA, Cao Y, et al. Tissue handling and specimen preparation in surgical pathology: issues concerning the recovery of nucleic acids from formalin-fixed, paraffin-embedded tissue. Arch Pathol Lab Med. 2008;132:1929-1935.
17. Nemeth SA, Lawrence N. Site identification challenges in dermatologic surgery: a physician survey. J Am Acad Dermatol. 2012;67: 262-268.
18. Federman DG, Concato J, Kirsner RS. Comparison of dermatologic diagnoses by primary care practitioners and dermatologists. A review of the literature. Arch Fam Med. 1999;8:170-172.

Most clinicians do a satisfactory job in choosing when and how to do a skin biopsy, but there is always room for improvement. The nine pointers provided here are based on standard-of-care practices and literature when available and also on the collective experience of the authors, who include a pathologist/dermatologist (JM), dermatopathologist (DZ), primary care physician (BR), and dermatologist/Mohs surgeon (EB).

1. CHOOSE YOUR BIOPSY TYPE WISELY
Using the appropriate type of biopsy can have the greatest effect on a proper diagnosis. The decision of which biopsy type to use is not always easy. The most common biopsy types are shave, punch, excisional, and curettage. Several reference articles detail each type of biopsy commonly used in primary care and how to perform them.^1,2

Each type of biopsy has inherent advantages and disadvantages. In general, the shave biopsy is most commonly used for lesions that are solitary and elevated and give the impression that a sufficient amount of tissue can be sampled with this technique. The punch biopsy is the best choice for most “rashes” (inflammatory skin disorders).² Excisional biopsy is used to remove melanocytic neoplasms or larger lesions. And curettage, while still used by some clinicians for melanocytic lesions because of its speed and simplicity, should almost never be used for diagnostic purposes.

Each technique is described in greater detail in the tips that follow.

Continue for tip #2 >>

 

2. WHEN PERFORMING A SHAVE BIOPSY, AVOID OBTAINING A SAMPLE THAT'S TOO SUPERFICIAL
The advantage of the shave biopsy is that it is minimally invasive and quick to perform. If kept small without compromising the amount of sample retrieved, the scars left by shave biopsies have the potential to blend well. The major disadvantage associated with the shave biopsy is that occasionally, if the shave is not deep enough, an insufficient amount of tissue is obtained. This can make it challenging to establish an accurate diagnosis.

Balancing the need to obtain adequate tissue with the desire to minimize scarring takes skill and experience. Taking a biopsy that is inadequate is a common occurrence. At times, the clinician’s clinical impression may be that a biopsy has obtained adequate tissue, when histologically only the superficial part of the skin surface has been sampled. This often is because of thickening of the superficial skin, whether as a manifestation of the anatomic site (eg, acral skin) or the disease process itself.

Unfortunately, this superficial skin often is nondiagnostic when unaccompanied by underlying epidermis and dermis. It is important to keep this in mind when you are obtaining a skin biopsy, especially when dealing with lesions that are very scaly or keratinized.

An equivocal biopsy wastes time, energy, and money, and it can negatively impact patient care.³ It can be difficult to balance practical aspects of the biopsy (ie, optimizing cosmetic outcomes, minimizing scarring and wound size) with the need to obtain sufficient tissue sampling (see Figure 1).

3. CHOOSE PUNCH OVER SHAVE BIOPSY FOR RASHES
In a punch biopsy, a disposable metal cylinder with a sharpened edge is used to “punch” out a piece of skin that can be examined under the microscope. Punch biopsy is the preferred technique for almost all inflammatory skin conditions (rashes) because the pathologist is able to examine both the superficial and deep portions of the dermis (see Figure 2).⁴  

Pathologists use the pattern of inflammation, in conjunction with epidermal changes, to distinguish different types of inflammatory processes. For example, lichen planus is typically associated with superficial inflammation, while lupus is known to have prominent superficial and deep inflammation.

An inadequate punch biopsy sample can hinder histologic assessment of inflammatory skin disorders that involve both the superficial and deep portions of the dermis and can make arriving at a definitive diagnosis more challenging. The diameter of a punch cylinder ranges from 1 to 8 mm. Smaller punch biopsies often create diagnostic challenges because they provide so little sample. A punch biopsy size of 4 mm is commonly used for rashes.

An advantage of the punch biopsy is that patients are left with linear scars rather than the round, potentially dyspigmented (darker or lighter) scars that are often associated with shave biopsy. A well-sutured punch biopsy can be cosmetically elegant, particularly if closure is oriented along relaxed skin tension lines. For this reason, punch biopsies are well suited for cosmetically sensitive locations (eg, the face), although shave biopsies are also often performed on the face.

Next page: Tip #4 >>

 

4. CHOOSE AN EXCISIONAL BIOPSY FOR A MELANOCYTIC NEOPLASM, WHEN POSSIBLE
The purpose of an excisional biopsy (which typically includes a 1- to 3-mm rim of normal skin around the lesion) is to completely remove a lesion. Excisional biopsy generally is the preferred technique for clinically atypical melanocytic neoplasms (ie, lesions that are not definitively benign).^4-8

When suspicion for melanoma is high, excisional biopsies should be performed with minimal undermining to preserve the accuracy of any future sentinel lymph node biopsy surgeries. Excisional biopsy is the most involved type of biopsy and has the largest potential for cosmetic disfigurement if not properly planned and performed. While guidelines from the American Academy of Dermatology state that “narrow excisional biopsy that encompasses [the] entire breadth of lesion with clinically negative margins to ensure that the lesion is not transected” is preferred, they also acknowledge that partial sampling (incisional biopsy) is acceptable in select clinical circumstances,⁹ such as when a lesion is large or on a cosmetically sensitive site (eg, the face).¹⁰

While a larger punch biopsy (6 or 8 mm) or even deep shave/saucerization may function as an excisional biopsy for very small lesions, this approach can be problematic. For one thing, these techniques are more likely than an excisional biopsy to leave a portion of the lesion in situ. Another concern is that a shave biopsy of a melanocytic lesion can lead to error or difficulty in obtaining the correct diagnosis on later biopsy.¹¹ For pathologists, small or incomplete samples make it challenging to establish an accurate diagnosis.¹² Among melanomas seen at a tertiary referral center, histopathologic misdiagnosis was more common with a punch or shave biopsy than with an excisional biopsy.⁹

It has been shown that partial biopsy for melanoma results in more residual disease at wide local excision and makes it more challenging to properly stage the lesion.^13,14 If a shave biopsy is used to sample a suspected melanocytic neoplasm, it is imperative to document the specific site of the biopsy, indicate the size of the melanocytic lesion on the pathology requisition form, and ensure that all (or nearly all) of the clinically evident lesion is sampled. Detailing the location of the lesion in the chart is not only essential in evaluating the present lesion, but it will serve you well in the future. Without knowing the patient’s clinical history, benign nevi that recur after a prior biopsy can be difficult to histologically distinguish from melanoma (see Figure 3). For more on this, see tip #7.

5. BE CAREFUL WITH CURETTAGE
Curettage is a biopsy technique in which a curette—a surgical tool with a scoop, ring, or loop at the tip—is used in a scraping motion to retrieve tissue from the patient. This type of biopsy often produces a fragmented tissue sample. Its continued use reflects the speed and simplicity with which it can be done. However, curettage destroys the architecture of the tissue of the lesion, which can make it difficult to establish a proper diagnosis, and therefore it is best avoided when performing a biopsy of a melanocytic lesion (see Figure 4).

Continue for tip #6 >>

 

6. REMEMBER THE IMPORTANCE OF PROPER FIXATION AND PROCESSING
As obvious as it may sound, it is important to remember to promptly place sampled tissue in an adequate amount of formalin so that the tissue is submersed in it in the container.¹⁵ Failure to do so can result in improper fixation and will make it difficult to render an appropriate diagnosis. Conventionally, a 10:1 formalin-volume-to-tissue-volume ratio is recommended. If the “cold time”—the amount of time a tissue sample is out of formalin—is too long (> a few hours), an appropriate assessment can be impossible.

Appropriate fixation and fixation times are important because molecular testing is being increasingly used to make pathologic diagnoses.¹⁶ Additionally, aggressively manipulating a biopsy sample while extracting it or placing it in formalin can cause “crush” artifact, which can limit interpretability (see Figure 5).

7. PROPERLY PHOTOGRAPH AND DOCUMENT THE BIOPSY LOCATION
When performing a biopsy of a suspicious neoplasm, clinicians often remove all of the lesion’s superficial components, which means that at the patient’s follow-up appointment and subsequent treatments, only a well-healed biopsy site will remain. The biopsy site may be so well healed that it blends seamlessly into the surrounding skin and is nearly impossible for the clinician to identify. This problem is seen most often when patients present for surgical excision or Mohs micrographic surgery.¹⁷

To properly record the site of a biopsy for future dermatologic exams, take pictures of the lesion at the time of biopsy. The photographs should clearly document the lesion in question and should be taken far enough from the site that surrounding lesions and/or other anatomic landmarks are also visible. Biangulation or triangulation (taking a series of two or three measurements, respectively, from the site of the lesion to nearby anatomic landmarks) can be used in conjunction with photographs.

When using measurements, be as specific and accurate as possible with anatomic terms. For example, measuring the distance from the “ear” is not helpful. It would be more helpful to measure the distance from the “tragus” or the “root of the helix.” Without a properly photographed and documented biopsy site, surgical treatment may need to be delayed until the location can be confirmed.

8. GIVE THE PATHOLOGIST A PERTINENT HISTORY
Providing the pathologist with a sufficient history, including the distribution and appearance of the lesion, and how long the patient has had it, can be essential in narrowing the diagnosis or making the differential diagnoses. Things like medication use or new exposures to perfumes, lotions, or plants can be especially helpful and are often overlooked when filling out the pathology requisition form.

When warranted, phone calls are helpful. You might, for example, call the pathologist and give him or her a more detailed physical examination description or additional pertinent history that was discovered after the requisition was filled out. Providing a good history can make the difference between a specific diagnosis and a broad differential.

Tip #9: Next page >>

 

9. KNOW WHEN TO REFER
There is no shame in asking for a second opinion when evaluating a skin lesion, especially with melanocytic neoplasms, where the stakes can be high, or skin eruptions that do not respond to conventional therapy. Remember, many cases are difficult, even for experts, and require a careful balance of clinical and histopathologic judgment.¹⁸

REFERENCES
1. Pickett H. Shave and punch biopsy for skin lesions. Am Fam Physician. 2011;84:995-1002.
2. Alguire PC, Mathes BM. Skin biopsy techniques for the internist. J Gen Intern Med. 1998;13:46-54.
3. Fernandez EM, Helm T, Ioffreda M, et al. The vanishing biopsy: the trend toward smaller specimens. Cutis. 2005;76:335-339.
4. Hieken TJ, Hernández-Irizarry R, Boll JM, et al. Accuracy of diagnostic biopsy for cutaneous melanoma: implications for surgical oncologists. Int J Surg Oncol. 2013;2013:196493.
5. Scolyer RA, Thompson JF, McCarthy SW, et al. Incomplete biopsy of melanocytic lesions can impair the accuracy of pathological diagnosis. Australas J Dermatol. 2006;47:71-75.
6. McCarthy SW, Scolyer RA. Pitfalls and important issues in the pathologic diagnosis of melanocytic tumors. Ochsner J. 2010;10:66-74.
7. Swanson NA, Lee KK, Gorman A, et al. Biopsy techniques. Diagnosis of melanoma. Dermatol Clin. 2002;20:677-680.
8. Chang TT, Somach SC, Wagamon K, et al. The inadequacy of punch-excised melanocytic lesions: sampling through the block for the determination of “margins.” J Am Acad Dermatol. 2009;60: 990-993.
9. Bichakjian CK, Halpern AC, Johnson TM, et al; American Academy of Dermatology. Guidelines of care for the management of primary cutaneous melanoma. American Academy of Dermatology. J Am Acad Dermatol. 2011;65:1032-1047.
10. Pardasani AG, Leshin B, Hallman JR, et al. Fusiform incisional biopsy for pigmented skin lesions. Dermatol Surg. 2000;26:622-624.
11. King R, Hayzen BA, Page RN, et al. Recurrent nevus phenomenon: a clinicopathologic study of 357 cases and histologic comparison with melanoma with regression. Mod Pathol. 2009;22:611-617.
12. Mills JK, White I, Diggs B, et al. Effect of biopsy type on outcomes in the treatment of primary cutaneous melanoma. Am J Surg. 2013;205:585-590.
13. Stell VH, Norton HJ, Smith KS, et al. Method of biopsy and incidence of positive margins in primary melanoma. Ann Surg Oncol. 2007;14:
893-898.
14. Egnatios GL, Dueck AC, Macdonald JB, et al. The impact of biopsy technique on upstaging, residual disease, and outcome in cutaneous melanoma. Am J Surg. 2011;202:771-778.
15. Ackerman AB, Boer A, Bennin B, et al. Histologic Diagnosis of Inflammatory Skin Disease: An Algorithmic Method Based on Pattern Analysis. New York, NY: Ardor Scribendi; 2005.
16. Hewitt SM, Lewis FA, Cao Y, et al. Tissue handling and specimen preparation in surgical pathology: issues concerning the recovery of nucleic acids from formalin-fixed, paraffin-embedded tissue. Arch Pathol Lab Med. 2008;132:1929-1935.
17. Nemeth SA, Lawrence N. Site identification challenges in dermatologic surgery: a physician survey. J Am Acad Dermatol. 2012;67: 262-268.
18. Federman DG, Concato J, Kirsner RS. Comparison of dermatologic diagnoses by primary care practitioners and dermatologists. A review of the literature. Arch Fam Med. 1999;8:170-172.

Most clinicians do a satisfactory job in choosing when and how to do a skin biopsy, but there is always room for improvement. The nine pointers provided here are based on standard-of-care practices and literature when available and also on the collective experience of the authors, who include a pathologist/dermatologist (JM), dermatopathologist (DZ), primary care physician (BR), and dermatologist/Mohs surgeon (EB).

1. CHOOSE YOUR BIOPSY TYPE WISELY
Using the appropriate type of biopsy can have the greatest effect on a proper diagnosis. The decision of which biopsy type to use is not always easy. The most common biopsy types are shave, punch, excisional, and curettage. Several reference articles detail each type of biopsy commonly used in primary care and how to perform them.^1,2

Each type of biopsy has inherent advantages and disadvantages. In general, the shave biopsy is most commonly used for lesions that are solitary and elevated and give the impression that a sufficient amount of tissue can be sampled with this technique. The punch biopsy is the best choice for most “rashes” (inflammatory skin disorders).² Excisional biopsy is used to remove melanocytic neoplasms or larger lesions. And curettage, while still used by some clinicians for melanocytic lesions because of its speed and simplicity, should almost never be used for diagnostic purposes.

Each technique is described in greater detail in the tips that follow.

Continue for tip #2 >>

 

2. WHEN PERFORMING A SHAVE BIOPSY, AVOID OBTAINING A SAMPLE THAT'S TOO SUPERFICIAL
The advantage of the shave biopsy is that it is minimally invasive and quick to perform. If kept small without compromising the amount of sample retrieved, the scars left by shave biopsies have the potential to blend well. The major disadvantage associated with the shave biopsy is that occasionally, if the shave is not deep enough, an insufficient amount of tissue is obtained. This can make it challenging to establish an accurate diagnosis.

Balancing the need to obtain adequate tissue with the desire to minimize scarring takes skill and experience. Taking a biopsy that is inadequate is a common occurrence. At times, the clinician’s clinical impression may be that a biopsy has obtained adequate tissue, when histologically only the superficial part of the skin surface has been sampled. This often is because of thickening of the superficial skin, whether as a manifestation of the anatomic site (eg, acral skin) or the disease process itself.

Unfortunately, this superficial skin often is nondiagnostic when unaccompanied by underlying epidermis and dermis. It is important to keep this in mind when you are obtaining a skin biopsy, especially when dealing with lesions that are very scaly or keratinized.

An equivocal biopsy wastes time, energy, and money, and it can negatively impact patient care.³ It can be difficult to balance practical aspects of the biopsy (ie, optimizing cosmetic outcomes, minimizing scarring and wound size) with the need to obtain sufficient tissue sampling (see Figure 1).

3. CHOOSE PUNCH OVER SHAVE BIOPSY FOR RASHES
In a punch biopsy, a disposable metal cylinder with a sharpened edge is used to “punch” out a piece of skin that can be examined under the microscope. Punch biopsy is the preferred technique for almost all inflammatory skin conditions (rashes) because the pathologist is able to examine both the superficial and deep portions of the dermis (see Figure 2).⁴  

Pathologists use the pattern of inflammation, in conjunction with epidermal changes, to distinguish different types of inflammatory processes. For example, lichen planus is typically associated with superficial inflammation, while lupus is known to have prominent superficial and deep inflammation.

An inadequate punch biopsy sample can hinder histologic assessment of inflammatory skin disorders that involve both the superficial and deep portions of the dermis and can make arriving at a definitive diagnosis more challenging. The diameter of a punch cylinder ranges from 1 to 8 mm. Smaller punch biopsies often create diagnostic challenges because they provide so little sample. A punch biopsy size of 4 mm is commonly used for rashes.

An advantage of the punch biopsy is that patients are left with linear scars rather than the round, potentially dyspigmented (darker or lighter) scars that are often associated with shave biopsy. A well-sutured punch biopsy can be cosmetically elegant, particularly if closure is oriented along relaxed skin tension lines. For this reason, punch biopsies are well suited for cosmetically sensitive locations (eg, the face), although shave biopsies are also often performed on the face.

Next page: Tip #4 >>

 

4. CHOOSE AN EXCISIONAL BIOPSY FOR A MELANOCYTIC NEOPLASM, WHEN POSSIBLE
The purpose of an excisional biopsy (which typically includes a 1- to 3-mm rim of normal skin around the lesion) is to completely remove a lesion. Excisional biopsy generally is the preferred technique for clinically atypical melanocytic neoplasms (ie, lesions that are not definitively benign).^4-8

When suspicion for melanoma is high, excisional biopsies should be performed with minimal undermining to preserve the accuracy of any future sentinel lymph node biopsy surgeries. Excisional biopsy is the most involved type of biopsy and has the largest potential for cosmetic disfigurement if not properly planned and performed. While guidelines from the American Academy of Dermatology state that “narrow excisional biopsy that encompasses [the] entire breadth of lesion with clinically negative margins to ensure that the lesion is not transected” is preferred, they also acknowledge that partial sampling (incisional biopsy) is acceptable in select clinical circumstances,⁹ such as when a lesion is large or on a cosmetically sensitive site (eg, the face).¹⁰

While a larger punch biopsy (6 or 8 mm) or even deep shave/saucerization may function as an excisional biopsy for very small lesions, this approach can be problematic. For one thing, these techniques are more likely than an excisional biopsy to leave a portion of the lesion in situ. Another concern is that a shave biopsy of a melanocytic lesion can lead to error or difficulty in obtaining the correct diagnosis on later biopsy.¹¹ For pathologists, small or incomplete samples make it challenging to establish an accurate diagnosis.¹² Among melanomas seen at a tertiary referral center, histopathologic misdiagnosis was more common with a punch or shave biopsy than with an excisional biopsy.⁹

It has been shown that partial biopsy for melanoma results in more residual disease at wide local excision and makes it more challenging to properly stage the lesion.^13,14 If a shave biopsy is used to sample a suspected melanocytic neoplasm, it is imperative to document the specific site of the biopsy, indicate the size of the melanocytic lesion on the pathology requisition form, and ensure that all (or nearly all) of the clinically evident lesion is sampled. Detailing the location of the lesion in the chart is not only essential in evaluating the present lesion, but it will serve you well in the future. Without knowing the patient’s clinical history, benign nevi that recur after a prior biopsy can be difficult to histologically distinguish from melanoma (see Figure 3). For more on this, see tip #7.

5. BE CAREFUL WITH CURETTAGE
Curettage is a biopsy technique in which a curette—a surgical tool with a scoop, ring, or loop at the tip—is used in a scraping motion to retrieve tissue from the patient. This type of biopsy often produces a fragmented tissue sample. Its continued use reflects the speed and simplicity with which it can be done. However, curettage destroys the architecture of the tissue of the lesion, which can make it difficult to establish a proper diagnosis, and therefore it is best avoided when performing a biopsy of a melanocytic lesion (see Figure 4).

Continue for tip #6 >>

 

6. REMEMBER THE IMPORTANCE OF PROPER FIXATION AND PROCESSING
As obvious as it may sound, it is important to remember to promptly place sampled tissue in an adequate amount of formalin so that the tissue is submersed in it in the container.¹⁵ Failure to do so can result in improper fixation and will make it difficult to render an appropriate diagnosis. Conventionally, a 10:1 formalin-volume-to-tissue-volume ratio is recommended. If the “cold time”—the amount of time a tissue sample is out of formalin—is too long (> a few hours), an appropriate assessment can be impossible.

Appropriate fixation and fixation times are important because molecular testing is being increasingly used to make pathologic diagnoses.¹⁶ Additionally, aggressively manipulating a biopsy sample while extracting it or placing it in formalin can cause “crush” artifact, which can limit interpretability (see Figure 5).

7. PROPERLY PHOTOGRAPH AND DOCUMENT THE BIOPSY LOCATION
When performing a biopsy of a suspicious neoplasm, clinicians often remove all of the lesion’s superficial components, which means that at the patient’s follow-up appointment and subsequent treatments, only a well-healed biopsy site will remain. The biopsy site may be so well healed that it blends seamlessly into the surrounding skin and is nearly impossible for the clinician to identify. This problem is seen most often when patients present for surgical excision or Mohs micrographic surgery.¹⁷

To properly record the site of a biopsy for future dermatologic exams, take pictures of the lesion at the time of biopsy. The photographs should clearly document the lesion in question and should be taken far enough from the site that surrounding lesions and/or other anatomic landmarks are also visible. Biangulation or triangulation (taking a series of two or three measurements, respectively, from the site of the lesion to nearby anatomic landmarks) can be used in conjunction with photographs.

When using measurements, be as specific and accurate as possible with anatomic terms. For example, measuring the distance from the “ear” is not helpful. It would be more helpful to measure the distance from the “tragus” or the “root of the helix.” Without a properly photographed and documented biopsy site, surgical treatment may need to be delayed until the location can be confirmed.

8. GIVE THE PATHOLOGIST A PERTINENT HISTORY
Providing the pathologist with a sufficient history, including the distribution and appearance of the lesion, and how long the patient has had it, can be essential in narrowing the diagnosis or making the differential diagnoses. Things like medication use or new exposures to perfumes, lotions, or plants can be especially helpful and are often overlooked when filling out the pathology requisition form.

When warranted, phone calls are helpful. You might, for example, call the pathologist and give him or her a more detailed physical examination description or additional pertinent history that was discovered after the requisition was filled out. Providing a good history can make the difference between a specific diagnosis and a broad differential.

Tip #9: Next page >>

 

9. KNOW WHEN TO REFER
There is no shame in asking for a second opinion when evaluating a skin lesion, especially with melanocytic neoplasms, where the stakes can be high, or skin eruptions that do not respond to conventional therapy. Remember, many cases are difficult, even for experts, and require a careful balance of clinical and histopathologic judgment.¹⁸

REFERENCES
1. Pickett H. Shave and punch biopsy for skin lesions. Am Fam Physician. 2011;84:995-1002.
2. Alguire PC, Mathes BM. Skin biopsy techniques for the internist. J Gen Intern Med. 1998;13:46-54.
3. Fernandez EM, Helm T, Ioffreda M, et al. The vanishing biopsy: the trend toward smaller specimens. Cutis. 2005;76:335-339.
4. Hieken TJ, Hernández-Irizarry R, Boll JM, et al. Accuracy of diagnostic biopsy for cutaneous melanoma: implications for surgical oncologists. Int J Surg Oncol. 2013;2013:196493.
5. Scolyer RA, Thompson JF, McCarthy SW, et al. Incomplete biopsy of melanocytic lesions can impair the accuracy of pathological diagnosis. Australas J Dermatol. 2006;47:71-75.
6. McCarthy SW, Scolyer RA. Pitfalls and important issues in the pathologic diagnosis of melanocytic tumors. Ochsner J. 2010;10:66-74.
7. Swanson NA, Lee KK, Gorman A, et al. Biopsy techniques. Diagnosis of melanoma. Dermatol Clin. 2002;20:677-680.
8. Chang TT, Somach SC, Wagamon K, et al. The inadequacy of punch-excised melanocytic lesions: sampling through the block for the determination of “margins.” J Am Acad Dermatol. 2009;60: 990-993.
9. Bichakjian CK, Halpern AC, Johnson TM, et al; American Academy of Dermatology. Guidelines of care for the management of primary cutaneous melanoma. American Academy of Dermatology. J Am Acad Dermatol. 2011;65:1032-1047.
10. Pardasani AG, Leshin B, Hallman JR, et al. Fusiform incisional biopsy for pigmented skin lesions. Dermatol Surg. 2000;26:622-624.
11. King R, Hayzen BA, Page RN, et al. Recurrent nevus phenomenon: a clinicopathologic study of 357 cases and histologic comparison with melanoma with regression. Mod Pathol. 2009;22:611-617.
12. Mills JK, White I, Diggs B, et al. Effect of biopsy type on outcomes in the treatment of primary cutaneous melanoma. Am J Surg. 2013;205:585-590.
13. Stell VH, Norton HJ, Smith KS, et al. Method of biopsy and incidence of positive margins in primary melanoma. Ann Surg Oncol. 2007;14:
893-898.
14. Egnatios GL, Dueck AC, Macdonald JB, et al. The impact of biopsy technique on upstaging, residual disease, and outcome in cutaneous melanoma. Am J Surg. 2011;202:771-778.
15. Ackerman AB, Boer A, Bennin B, et al. Histologic Diagnosis of Inflammatory Skin Disease: An Algorithmic Method Based on Pattern Analysis. New York, NY: Ardor Scribendi; 2005.
16. Hewitt SM, Lewis FA, Cao Y, et al. Tissue handling and specimen preparation in surgical pathology: issues concerning the recovery of nucleic acids from formalin-fixed, paraffin-embedded tissue. Arch Pathol Lab Med. 2008;132:1929-1935.
17. Nemeth SA, Lawrence N. Site identification challenges in dermatologic surgery: a physician survey. J Am Acad Dermatol. 2012;67: 262-268.
18. Federman DG, Concato J, Kirsner RS. Comparison of dermatologic diagnoses by primary care practitioners and dermatologists. A review of the literature. Arch Fam Med. 1999;8:170-172.