Tumor of follicular infundibulum is Basal cell carcinoma

Tumor of follicular infundibulum (TFI) is currently thought to be a benign epithelial neoplasm with follicular differentiation. It is encountered commonly in association with basal cell carcinoma (BCC), often as an incidental finding. We reexamined 24 cases of TFI and noted, often only focally, many changes typical of BCC, including palisading of cells at the periphery of aggregations, germinative cells, follicular germs in the absence of a follicular papilla, crowding of cells, individual necrotic neoplastic cells, fibromucinous stroma, and clefts between aggregations of neoplastic cells and stroma. Five cases were associated with BCC, and 2 of them showed obvious continuity between both types of lesions. Moreover, we observed recurrences of what seemed to be a completely removed BCC in which tiny columns of cells typical of TFI were present in surgical margins. Those findings prompted us to conclude that TFI may be one of many manifestations of BCC rather than a differential diagnosis of it.