Granular Cell Basal Cell Carcinoma

Abstract

Granular cell basal cell carcinoma (BCC), characterized by large cells with abundant eosinophilic cytoplasm and conspicuous granularity, is an extremely rare variant of BCC with only 14 cases reported in the literature to date. A case of an 82-year-old man with clinically suspected BCC of the face is presented. Microscopic examination demonstrated characteristic morphologic and immunophenotypic features of granular cell BCC, as well as novel expression of p16 and lack of bcl-2 expression, both of which are previously undescribed in granular BCCs in the literature to date. Although very rare, this entity is important to include in the differential of any nodular cutaneous neoplasm with granular features. The rarity of this lesion makes immunohistochemistry especially helpful. As in other BCCs, granular cell BCCs typically strongly express Ber-EP4 and cytokeratins. The granular BCCs are characteristically periodic acid-Schiff positive, but show no expression of S100 protein. The rarity of the granular cell BCC and the aggressive biological behavior of the entities that may share similar histologic features make arriving at the correct diagnosis paramount to appropriate clinical management. The fifteenth case of granular cell BCC with subsequent review of the literature is reported, with particular focus on the immunohistochemical characteristics.