Track: Case Reports

Abstract:

Spindle cell–predominant trichodiscoma (SCPT) is a rare, benign, hamartomatous adnexal neoplasm that arises from the mantle of the hair follicle. Previously referred to as S100-negative neurofollicular hamartoma, SCPT typically presents as solitary or multiple papules, often on the face with a predilection for the nose. Histologically, these lesions are characterized by bland spindle cells arranged in fascicles with variable myxoid and collagenous stroma and a minimal epithelial component. We report an unusual case of SCPT associated with perineurial differentiation, as evidenced by a unique immunoprofile including diffuse GLUT-1 expression in a subset of lesional cells. A 52-year-old man presented with a longstanding nasal lesion. Histopathologic evaluation revealed a multilobular dermal spindle cell proliferation with whorled and storiform architecture, alternating hypercellular and hypocellular regions, and mixed collagenous and myxoid stroma. Lesional cells in larger, less cellular nodules showed diffuse CD34 and focal weak EMA positivity, while lesional cells in smaller, more cellular nodules exhibited diffuse GLUT-1, with a surrounding rim of CD34-positive cells. No expression of S100, SOX10, PRAME, or STAT6 was observed. Next-generation sequencing for sarcoma-associated fusions was negative. This case highlights a novel phenotypic feature of SCPT and expands the known immunophenotypic spectrum to include perineurial differentiation.