REPORT OF A CASE
A 43-year-old woman had a slowly enlarging, painful, bleeding scalp nodule for five to ten years. She stated that she had fallen on the area many years before. She was otherwise in good health and was receiving no medication. There was no family history of skin disease.Physical examination revealed a 1.2 × 1.2-cm friable, focally ulcerated, erythematous, crusted scalp nodule (Fig 1). An excisional biopsy was performed, revealing a well-circumscribed, dark-brown, granular nodule extending to adipose tissue (Fig 2).Histologic examination showed a well-circumscribed nodule continuous with the epidermis, consisting of squamous lobules with abrupt keratinization and intense melanin deposition. There were foci of increased mitoses and a mild degree of nuclear atypia (Figs 3 through 5).What is your diagnosis?
Proliferating trichilemmal tumor.
Proliferating trichilemmal tumor is an uncommon neoplasm of outer root sheath cells. It
Carlin MC, Bailin PL, Bergfeld WF. Enlarging, Painful Scalp Nodule. Arch Dermatol. 1988;124(6):937-938. doi:10.1001/archderm.1988.01670060083023