Report of Basal Cell Carcinoma Occurring With a Desmoplastic Trichilemmoma Successfully Treated With Mohs Micrographic Surgery

Desmoplastic trichilemmoma, an uncommon variant of trichilemmoma, is a benign adnexal neoplasm originating from the outer root sheath of a hair follicle, which has rarely been associated with atypical basaloid proliferations, including basal cell carcinoma. In this patient case, a 67-year-old female presented to our dermatology clinic for a skin check. On physical examination, a pearly, pink papule was noted on the vertex scalp, and a biopsy was obtained to rule out malignancy. Histologic examination of the lesion favored a desmoplastic trichilemmoma; however, a basaloid neoplasm could not be ruled out. Subsequently, the patient underwent Mohs micrographic surgery, and upon examination of the Stage I Mohs slides, superficial basal cell carcinoma was identified within the lesion. This case serves to further strengthen the known association between basal cell carcinoma and desmoplastic trichilemmoma. In addition, it demonstrates that the presence of basal cell carcinoma may not be observed on the initial biopsy of these lesions, underscoring the utility of complete surgical excision.