Tumor of the follicular infundibulum: a clinicopathologic study.

BACKGROUND: Tumor of the follicular infundibulum (TFI) is a rare benign adnexal tumor that has characteristic histopathologic features.

OBJECTIVE: Our purpose was to describe the clinical and pathologic features of 12 patients with TFI.

METHODS: Of 121,500 cutaneous biopsy specimens recorded between 1981 and 1993, all TFIs were identified and examined by conventional microscopy. The clinical and histologic findings were compared with those of previously published cases.

RESULTS: Of the 12 patients, seven had a solitary tumor, two had eruptive TFI involving the face, and three TFIs were incidentally discovered in association with nevus sebaceus or fibroma. TFI-like changes were also observed in the wall of a hybrid cyst. The most discriminating features of TFI were the horizontal platelike organization of the tumor and the dense elastic network beneath the tumor. Of the different forms of TFI, only eruptive tumors can be clinically identified because they are small hypopigmented macules.

CONCLUSION: We classify TFIs as (1) solitary tumors, (2) eruptive tumors, (3) TFI associated with other lesions of Cowden's disease, (4) TFI associated with a single tumor such as nevus sebaceus, and (5) TFI-like epidermal changes.