Eruptive tumors of the follicular infundibulum presenting as hypopigmented macules on the buttocks of two Black African males

Abstract

We report two cases of eruptive tumors of the follicular infundibulum (TFI) with an unusual clinical presentation which has not been described previously in literature. In both cases, the appearance was strikingly similar, consisting of multiple asymptomatic hypopigmented macules on the buttocks of two Black African males, aged 38 and 55 years old. In both cases, the eruption had evolved over several months. The individual lesions were of similar size, approximately 1 cm, with irregular and ill-defined borders. Histopathological examination revealed a superficial and horizontal plate-like proliferation of keratinocytes emanating from the epidermis with multiple slender attachments. Pale keratinocytes were present within the epithelial plates. A Fontana stain showed a loss of melanin pigment from the epithelial plates. Orcein (elastic) stain highlighted an increase of the number of the elastic fibers surrounding the tumor. On the basis of these findings, a diagnosis of eruptive TFI was established for both cases. Among the various presentations of TFI, only the eruptive variant appears to be clinically distinctive, with asymptomatic hypopigmented macules usually located on the face, neck and upper trunk. Eruptive TFI should also be added to the clinical differential diagnosis of multiple hypopigmented macules on the buttocks of Black patients.

Tumor of follicular infundibulum: An unsuspected cause of macular hypopigmentation

“…[1,2,4] Clinically, most cases are diagnosed as either basal cell carcinoma or seborrhoeic keratosis. [2,3] The eruptive form is much less frequent in comparison to the solitary variant. In the two largest series available in the literature the eruptive variant constituted 6% [4] and 7.7%, [1] respectively, of all cases.…”

“…[1] Uncommonly, it occurs on the buttocks and extremities. [3,5] In two isolated case reports, the lesions also involved vulva and intertriginous areas, respectively. [3] Classically, it presents as symmetrically distributed hypopigmented, pale pink to flesh colored and less commonly erythematous, either flat macular, depressed lesions, or papules.…”

“…[2] Histopathologically, tumor of follicular infundibulum-like reactive epidermal changes have been seen as an incidental finding with fibrous histiocytoma, basal cell carcinoma, seborrhoeic keratosis, actinic keratosis, squamous cell carcinoma, melanoma in situ, desmoplastic melanoma, junctional melanocytic nevus, lentigo, hybrid cyst (with features of epidermoid and trichilemmal cyst), epidermal inclusion cyst, epidermoid cyst, trichilemmoma and tinea versiclor. [1,3,4] We report three cases of an uncommon eruptive form of tumor of follicular infundibulum presenting as hypopigmented lesions.…”

Histologic Mimics of Basal Cell Carcinoma

“…80 Elastin stains may demonstrate an elastin fiber network at the base of the lesion. 48,79,80 Squamous Cell Carcinoma Squamous cell carcinoma may be challenging to distinguish from BCC in limited biopsies. Ber-EP4 is commonly employed to assist in this distinction, with strong expression in BCC and absent expression in squamous cell carcinoma (Table).…”

“…48,[76][77][78] Although TFI may be misinterpreted as superficial BCC, TFI lacks cytologic atypia, myxoinflammatory stroma, peripheral clefting, and significant mitotic activity (Table). 48,[76][77][78][79] Unlike BCC, TFI displays colonizing CK20…”