Tumor of the follicular infundibulum with sebaceous differentiation

Background: Tumor of the follicular infundibulum (TFI) is a relatively rare tumor which clinically presents as a solitary keratotic papule usually on the head and neck which on microscopic examination typically reveals a plat e-like fenestrated epithelial tumor composed of pale staining cells. Methods: We describe a new variant of TFT. An 80-year-old male with a histo ry of multiple basal cell carcinomas and a squamous cell carcinoma presente d with a 2-year history of a red, scaly, slightly elevated plaque on the la teral aspect of his right buttock. Results: Histopathological examination revealed plate-like reticulate epith elial outgrowths of large and pale cells with foci of sebaccous differentia tion and numerous colloid bodies. Differential diagnosis included superfici al basal cell carcinoma with sebaceous and ductal differentiation, tumor of the follicular infundibulum, an unusual fibroepithelioma of Pinkus or an e ccrine fibroadenoma with sebaccous differentiation. Conclusion: This case illustrates a hybrid adnexal tumor with histologic fe atures common to both tumor of the follicular infundibulum and superficial epithelioma with sebaccous differentiation.