Signet‐ring clear‐cell basal cell carcinoma

Basal cell carcinoma displays a myriad of histopathologic variants, some of which are related to the different lines of differentiation, vis-a-vis, squamous, pilar, eccrine, or sebaceous. We herein report an example of a rare signet-ring, clear-cell variant. Our diagnosis is primarily based on the histopathologic features of the tumor, namely, the dermal nests of tumor cells with peripheral palisading and focally retracted fibroblastic stroma. Several nests are folliculocentric. The tumor cells are glycogen-rich, mucin-negative, pankeratin-positive, cytokeratin-negative, S100 protein-negative, and carcinoembryonic antigen-negative. Based on the histopathology and the results of the special stains we propose that the signet-ring clear-cell variant of basal cell carcinoma is differentiating in the direction of the outer root sheath cells of the pilar structure.