Track

Case Reports

Abstract

A 57-year-old male with Fitzpatrick Type V skin presented to dermatology for a slowly growing, asymptomatic, isolated dark papule on his right lower leg. Dermatologic exam revealed a solitary 0.5 cm sharply demarcated round, brown-black subtly keratotic papule; dermoscopic exam demonstrated milky red globules and polymorphous vessels with intervening blue-white areas and overlying scale. Differential diagnosis included squamous cell carcinoma vs. pigmented basal cell carcinoma vs. dermatofibroma, and tangential biopsy was performed. Histopathology demonstrated a hyperkeratotic endophytic proliferation of basaloid and squamous cells with scattered squamous eddies, consistent with an inverted follicular keratosis (IFK). Given histopathology supported a benign diagnosis, and shave biopsy resulted in gross removal of the IFK, the patient was provided reassurance with no additional treatment recommendations. IFK is a rare, benign follicular tumor, classically presenting on the head or neck and generally diagnosed histopathologically, given its clinically mimicking other benign and even malignant neoplasms. Previously described dermoscopic features include central white-yellow amorphous area, milky red globules, radial hairpin vessels, and scale. A brief literature review of recent reports of IFK revealed few cases, with almost all occurring on the head and neck; no cases specified the presence in a patient with skin of color. Notably, several reported successful treatment with imiquimod. We highlight this unique case of IFK on the leg of a patient with skin of color. Though rare, IFK should be considered in the differential diagnosis for lesions clinically resembling keratinocyte carcinoma, given its variable clinical and dermoscopic appearance.