Abstract
Abstract Introduction/Objective Basal cell carcinoma (BCC) is a commonly encountered dermatologic entity by general surgical pathologists and dermatopatholgists alike and usually does not pose a diagnostic dilemma. However, BCC can take on a variety of histopathologic morphologies, sometimes mimicking more malignant entities. We present an unusual case of BCC with a rare morphology. Methods A 56-year-old male with history of non-melanoma skin cancer presented to his dermatologist with a 5mm pink, pearly, papule on his left forearm. A biopsy was performed, and histology and immunohistochemistry was utilized to evaluate and characterize the neoplasm. Results H&E stained histopathologic sections demonstrated an unusual epithelioid neoplasm with infiltrative growth, peripheral palisading of atypical basaloid cells, and areas of prominent rhabdoid/plasmacytoid cytology reminiscent of myoepithelial cells. The neoplasm was diffusely positive for Ber-Ep4 while SMA highlighted the areas with rhabdoid/plasmacytoid appearance. Mart-1 and SOX-10 were positive in only a few bland intralesional melanocytes. Conclusion The histological appearance was concerning for melanoma with rhabdoid morphology or an unusual variant of basal cell carcinoma. Positive Ber-Ep4 staining supported the histological impression of an unusual basal cell carcinoma variant while staining for SMA supported the impression of myoepithelial differentiation. Myoepithelial differentiation is extremely rare in BCC with only 16 prior cases described in the literature. To our knowledge, this is the first reported case of BCC with myoepithelial differentiation presenting outside the face. Consequently, this is an important diagnostic differential to consider when evaluating epithelial neoplasms with rhabdoid or plasmacytoid morphology.
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