Pigmented tumor in the nostril

Abstract

A 64-year-old man was noted to have a single pigmented lesion in the nostril of his nose. Clinical examination revealed a 5 mm nodular growth and brown lesion. With a presumed clinical diagnosis of malignant skin tumor, a biopsy was performed. The histological examination revealed the unexpected diagnosis of pigmented inverted follicular keratosis.The inverted follicular keratosis is an uncommon benign lesion that is usually diagnosed histologically rather than clinically. It commonly simulates other proliferative skin lesions.

Pigmented inverted follicular keratosis masquerading as basal cell carcinoma

“…However now, it is considered a benign tumor originating from follicular infundibulum. [ 1 2 ] Most known cases are of nonpigmented type, presenting as solitary skin colored or pink papule, plaque, or nodule. We present a rare case of pigmented IFK.…”

“…[ 1 ] Pigmented variant is known and the color of the lesion may range from yellow to brown to black, depending on melanin content. [ 2 ] Thus, it may mimic many cutaneous conditions including seborrheic keratosis, melanoacanthoma, squamous cell carcinoma, basal cell carcinoma, and melanoma. [ 2 3 ] Not surprisingly, the diagnosis of IFK is often missed clinically and reveals itself on histopathology.…”

“…[ 2 ] Thus, it may mimic many cutaneous conditions including seborrheic keratosis, melanoacanthoma, squamous cell carcinoma, basal cell carcinoma, and melanoma. [ 2 3 ] Not surprisingly, the diagnosis of IFK is often missed clinically and reveals itself on histopathology. Differentiating IFK from irritated seborrhoeic keratosis (SK) is difficult.…”