Sarcomatoid salivary duct carcinoma of the parotid gland.

Salivary duct carcinoma (SDC) is a high-grade neoplasm known to histologically resemble high-grade ductal carcinoma in situ of the breast. We describe 3 cases of sarcomatoid salivary duct carcinoma, a heretofore unreported variant of SDC. Each case was a composite of SDC and sarcomatoid carcinoma and histologically similar to reported cases arising in the breast. The clinicopathologic features, including immunohistochemistry, of 3 cases were investigated. In the 3 men, ages 56, 68, and 70 years, the resected parotid tumors measured 1.5, 3.5, and 1.5 cm, respectively. Only the 3.5-cm tumor extended beyond the parotid gland into soft tissue. This patient died at 3 years with pulmonary metastases. The other patients were free of disease at 6 and 12 months. Histologically, each case was a composite of usual-type SDC and sarcomatoid carcinoma. SDC showed typical cribriform architecture, whereas anaplastic, spindled cells constituted the sarcomatoid areas. Immunohistochemically, epithelial elements stained as follows: cytokeratin (AE1/AE3 & CAM 5.2) positive in 3 of 3 cases, EMA positive in 3 of 3 cases, vimentin negative in 3 of 3 cases, desmin negative in 3 of 3 cases, c-erbB-2 positive in 1 of 2 cases. Sarcomatoid elements stained as follows: AE1/AE3 negative in 3 of 3 cases, CAM 5.2 rare positive cell in 1 of 3 cases, EMA focally positive in 3 of 3 cases, vimentin positive in 3 of 3 cases, desmin negative in 3 of 3 cases, c-erbB-2 negative in 2 of 2 cases. Electron microscopy, performed in one case, showed scattered junctional complexes congruent with epithelial differentiation. Immunohistochemical results, EMA and CAM 5.2 positivity, and ultrastructural findings supported our belief that these unique biphasic tumors represented SDC with sarcomatoid carcinoma. We conclude an element of sarcomatoid carcinoma rarely may arise in association with SDC, and it is erroneous to diagnose such tumors as "carcinosarcoma."