Solitary and multiple tumors of follicular infundibulum: a review of 168 cases with emphasis on staining patterns and clinical variants

Abstract

Tumor of the follicular infundibulum (TFI) is an uncommon benign adnexal tumor that usually presents as a solitary keratotic papule in the head and neck area. Infrequently, it may present as multiple lesions or in association with other conditions. Although it was initially described in 1961, the pathogenesis of this lesion is still controversial. The clinical and histologic features of 168 cases of TFI were reviewed. Random cases were stained with elastic Van Gieson, cytokeratin (CK)20 and Ber-EP4. Clinical data and clinical images were collected. The median age at presentation was 66 years with a slight female predominance. As subset of patients (7.7%) had multiple TFI, some of which presented with hypopigmented lesions of the head and neck area. TFI has a unique staining pattern; all cases tested showed a brush-like network of elastin fibers, no cases stained for Ber-EP4 and 91.7% of cases show single cell positivity to CK20. This is in contrast to basal cell carcinoma used for comparison purposes. TFI is a distinct neoplastic entity with a unique staining pattern and variable clinical presentation. One should be aware of the potential clinical presentation of multiple TFI as hypopigmented lesions especially in the head and neck area.