Case Report

An excisional biopsy of a skin papule was taken of the left cheek from a 45-year-old man. The asymptomatic lesion has been present for an unknown period of time.

Figure 1

Figure 1: Low power photomicrograph shows a well-circumscribed dermal nodule composed of epithelial components within a fibromyxoid stroma.

Figure 2

Figure 2: Higher power photomicrograph shows the epithelial component forming branching tubules, ducts and dilated cystic spaces containing eosinophilic acellular material. The stroma in between the epithelial elements is fibrotic, loose, and focally myxoid.

Diagnosis: Cutaneous mixed tumor

Comment

Cutaneous mixed tumor is an uncommon, benign adnexal neoplasm arising from apocrine or eccrine glands of the dermis. The tumor predominantly affects middle-aged women and presents as a slowly growing, painless, firm papule or nodule, most often involving the head and neck[₁]. Histologically, the tumor is well-circumscribed and shows a biphasic growth pattern: an epithelial component and a stromal component having myxoid, fibrous, or chondroid differentiation. The epithelial component is composed of trabeculae, tubules, or ducts. Classification into eccrine or apocrine type is based on the epithelial lining cells of the sweat duct lumina. Immunohistochemical analysis of apocrine mixed tumors shows various staining patterns similar to the those of hair follicles, sebaceous glands, and all components of apocrine glands (folliculosebaceous-apocrine unit)[₂].

While mixed tumor of the skin is almost invariably benign, cases with cytologic atypia or malignancy are reported in the literature [₃, ₄]. Kazakov et al. reported a series of 18 apocrine mixed tumors of the skin with architectural or cytologic atypia. The tumors ranged in size from 4 mm to 12 cm. The lesions showed good circumscription and lack of capsular breach or hypercellularity. However, some asymmetry and infiltrative and pushing borders were seen. The tumors were all excised. At a mean follow-up of 5 years, no recurrences or metastases were found.

Complete excision is the treatment of choice. Tumors with infiltrative borders can recur following excision, however.

Correspondence to

Susan Repertinger, M.D. Department of Pathology Creighton University Medical Center Omaha Nebraska USA srepertinger@creighton.edu