Abstract

Cutaneous malignant mixed tumor (MMT) is an extremely rare, high-grade adnexal neoplasm with increased risk for local recurrence and distant metastases with fewer than 50 cases reported in the literature. MMT may arise de novo or, less frequently, from malignant transformation of its benign counterpart, a chondroid syringoma. We report a case of cutaneous MMT arising from a chondroid syringoma occurring on the foot of a 57-year-old African American male, clinically suspected to be a ganglion cyst. Gross examination revealed a 2.0 cm cyst-like lesion. Histologic examination revealed a relatively well-circumscribed nodule composed of atypical epithelioid cells with pleomorphic nuclei arranged in anastomosing trabeculae with foci of increased cellularity, loss of cohesion, and focal ductal differentiation. The stroma was variably myxoid and cartilaginous, and angiolymphatic invasion was present. Focal bland-appearing epithelial cells with ductal differentiation and myxoid stroma were present at the periphery consistent with benign chondroid syringoma. By immunohistochemistry, the atypical epithelioid cells demonstrated strong positive staining for cytokeratin AE1/3 and S-100 and focal positive staining for EMA. This case emphasizes the importance of thorough histologic examination of atypical adnexal tumors to attempt to identify both benign counterparts and diagnostic features of malignancy. The presence of benign elements and angiolymphatic invasion at the periphery of this lesion confirmed the diagnosis of MMT arising from malignant transformation of a chondroid syringoma, drastically altering patient prognosis. MMT requires wide local excision, consideration for adjuvant therapy, and continued long-term clinical follow-up due to its potentially aggressive clinical behavior.

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