Dermoscopy revealed an 8-mm scaly brown-black papule that lacked melanocytic features (pigment network, globules, streaks, or homogeneous blue or brown color) but had milia-like cysts and so-called “fat fingers” (short, straight to curved radial projections1). These findings were consistent with a diagnosis of seborrheic keratosis (SK).
SKs go by many names and are often confused with nevi. Some patients might know them by such names as “age spots” or “liver spots.” Patients often have many SKs on their body; the back and skin folds are common locations. Patients may be unhappy about the way they look and may describe occasional discomfort when the SKs rub against clothes and inflammation that occurs spontaneously or with trauma.
Classic SKs have a well-demarcated border and waxy, stuck-on appearance. There are times when it is difficult to distinguish between an SK and a melanocytic lesion. Thus, a biopsy may be necessary. In addition, SKs are so common that collision lesions may occur. (Collision lesions result when 2 histologically distinct neoplasms occur adjacent to each other and cause an unusual clinical appearance with features of each lesion.) The atypical clinical features in a collision lesion may prompt a biopsy to exclude malignancy.
Dermoscopic features of SKs include well-demarcated borders, milia-like cysts (white circular inclusions), comedo-like openings (brown/black circular inclusions), fissures and ridges, hairpin vessels, and fat fingers.
Cryotherapy is a quick and efficient treatment when a patient would like the lesions removed. Curettage or light electrodessication may be less likely to cause post-inflammatory hypopigmentation in patients with darker skin types. These various destructive therapies are often considered cosmetic and are unlikely to be covered by insurance unless there is documentation of significant inflammation or discomfort. In this case, the lesion was not treated.
Photos and text for Photo Rounds Friday courtesy of Jonathan Karnes, MD (copyright retained). Dr. Karnes is the medical director of MDFMR Dermatology Services, Augusta, ME.