Lipomatous mixed tumor with follicular differentiation of the skin

Abstract

A very rare case of cutaneous mixed tumor with numerous adipose tissue and hair follicular structures in a 67-year-old Japanese male was reported. A well-circumscribed tumor was in the subcutaneous tissue of the cheek and far from the parotid gland. Histologically, the tumor consisted of an admixture of the adipose tissue, fibromyxoid tissue with spindle cells, and branching tubular structures. Outer layers of ductal epithelial cells and single spindle cells were often in a transition, likely as typical mixed tumor. Branching ducts connected with keratinous cysts, strands of trichoblastic basophilic cells and clear cell nests. There was a gradual transition, between small-sized adipocytes and vacuolated spindle cells. No chondroid stroma was seen. To our knowledge, this tumor is the first case of a lipomatous mixed tumor with hair follicular differentiation. The case indicates an additional wide spectrum of histologic appearances of cutaneous mixed tumor.