Eccrine porocarcinoma (EPC), originally described by Pinkus and Mehregan1 in 1963, is an exceedingly rare sweat gland tumor most commonly seen in older patients. Fewer than 300 cases have been reported in the literature, and it is believed to represent only 0.005% to 0.01% of cutaneous malignancies.2 In the absence of established guidelines, wide local excision (WLE) has traditionally been considered the standard of treatment; however, local recurrence and nodal metastasis rates associated with WLE have been reported as high as 20%.3 More recently, a number of case reports and small case series have demonstrated higher cure rates with Mohs micrographic surgery (MMS), though follow-up is limited.3-5 We describe a case of EPC presenting as a recurrent wart in a 36-year-old man that was successfully treated with MMS.
Case Report
A 36-year-old man with no notable medical history presented with a 0.5×0.5-cm, asymptomatic, flesh-colored, hyperkeratotic, polypoid papule on the right medial thigh (Figure 1). The lesion was diagnosed as a wart and treated with cryotherapy by another dermatologist several years prior to presentation. Dermatoscopic examination at the current presentation showed a homogenous yellow center with a few peripheral vessels and a faint pink-tan halo (Figure 2). Our differential diagnosis included a recurrent wart, fibrosed pyogenic granuloma, irritated intradermal nevus, skin tag, and adnexal neoplasm. A shave biopsy was performed. Histopathologic analysis revealed multiple aggregations of mildly pleomorphic epithelial cells emanating from the epidermis, with many aggregations containing ductal structures (Figure 3). Rare necrotic and pyknotic cells were present, but no mitotic figures or lymphovascular invasion were identified. Immunohistochemical staining was positive for carcinoembryonic antigen and epithelial membrane antigen but negative for Ber-EP4. These findings were consistent with a well-differentiated EPC.
Figure 1. A 0.5×0.5-cm, flesh-colored, hyperkeratotic, polypoid papule on the right medial thigh.
Figure 2. Dermatoscopic examination showed a homogenous yellow center with a few peripheral vessels and a faint pink-tan halo.
Figure 3. A, Histopathology revealed an exophytic and endophytic neoplasm emanating from the epidermis that consisted of epithelial crowded aggregations that were jagged in outline and irregular in shape (H&E, original magnification ×20). B, The ducts within the aggregations varied in size (H&E, original magnification ×200).
The patient was offered MMS or WLE, with or without sentinel lymph node biopsy (SLNB). He opted for MMS. The initial 1-cm margin taken during MMS was sufficient to achieve complete tumor extirpation, and the final 3.7×2.5-cm defect was closed primarily. The MMS debulking specimen was sent for permanent sectioning and showed a small focus of residual tumor cells, but no mitoses or lymphovascular invasion were seen. The patient was referred to surgical oncology to discuss the option of SLNB, which he ultimately declined. He also was offered regional or whole-body positron emission tomography–computed tomography (PET-CT) to rule out metastatic disease, which he also declined. There was no evidence of recurrence or lymphadenopathy 19 months postoperatively.