Track

Abstract

A 76 year old man with a history of well-controlled psoriasis on deucravacitinib and no prior skin cancer history presented with a several-week history of an increasingly bothersome scalp lesion. Physical examination revealed a 12 mm pink to brown plaque on the left vertex scalp. Histologic sections from a shave biopsy of the lesion revealed a diffuse dermal proliferation of spindle cells within a collagenous stroma.  Dense, pink collagen forming “doughnut-like” structures around blood vessels were seen throughout the lesion.  On high power examination, the spindled cells had notable nuclear pleomorphism, hyperchromasia, and atypical mitotic figures. Immunohistochemical stains for Sox10, S100 protein, p40, and pankeratin were negative, excluding sarcomatoid squamous cell carcinoma and melanoma and a diagnosis of atypical fibroxanthoma (AFX) was rendered. The patient was subsequently treated with mohs surgery. Collagen “doughnut-like” structures surrounding vasculature are a fairly common occurrence in dermatofibroma (DF) histopathology. They are not often present in AFX except for the rare keloidal variant. Cytological atypia should lead to proper staining and diagnosis. Dermatopathologists should be aware of this unusual variant of atypical fibroxanthoma and potential resemblance to benign entities at low power.