Abstract:

Malignant mixed tumor (MMT) of the skin is an extremely rare high-grade adnexal neoplasm with a metastasis rate of 45% and the mortality rate of 22%. To date less than 50 cases have been reported in the literature. The tumor usually presents as a flesh colored or erythematous nodule on the distal extremities of middle-aged patients with a female predilection. Although the diagnosis depends on the presence of the mucoid stroma or chondroid differentiation, the malignancy relates only to the epithelial component. Herein we describe a case of an 86-year-old female presented with a recurrent painful mass of the left great toe. Magnetic resonance imaging showed a 2.4 cm soft tissue mass along medial aspect of distal phalanx of the great toe with erosion and cystic changes. The disarticulation specimen showed a 2.4 cm ill-defined, soft, and glistening tan-white dermal and subcutaneous mass invading distal phalanx and surrounding soft tissue. Microscopic sections revealed a biphasic multinodular neoplasm with infiltrative growth pattern involving the skin, deep subcutaneous tissue, and distal phalanx with a 1 cm free resection margin. The tumor had a variegated growth pattern consists of solid nodules and infiltrative glandular structures in a chondroid mesenchymal component. The epithelial component demonstrated moderate cytologic atypia with up to 12 mitoses per 10 HPF. Focal perineural invasion with no evidence of angiolymphatic invasion or tumor necrosis was appreciated. She was free of recurrence at 2-year follow up. Due to the potential aggressive behavior of this tumor, wide local excision and long-term follow up is recommended. Therefore, pathologists should be aware of this rare but malignant entity to guide the management.

Financial Disclosure:
No current or relevant financial relationships exist.

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Samira Mortazavi, MD