Primary oncocytic carcinoma of the salivary glands: a clinicopathologic and immunohistochemical study of 12 cases.

Oncocytic carcinoma (OC) of salivary gland origin is an extremely rare proliferation of malignant oncocytes with adenocarcinomatous architectural phenotypes, including infiltrative qualities. To help clarify the clinicopathologic and prognostic features of this tumor group, herein, we report 12 OC cases arising from the salivary glands, together with follow-up data and immunohistochemical observations. There were 10 males and 2 females with an age range of 41 to 86 years (median age: 61.3 years). Most occurred in the parotid gland (10/12) with one in the palate and one in the retromolar gland. The tumors were unencapsulated and often invaded into the nearby gland, lymphatic tissues and nerves. The neoplastic cells had eosinophilic granular cytoplasm and round vesicular nuclei with prominent red nucleoli. Ultrastructural study, PTAH, and immunohistochemistry staining confirmed the presence of numerous mitochondria in the cytoplasm of oncocytes. Cellular atypia and pleomorphism varied in the current series. Double nuclei and mitoses were observed in some cases, while one case that showed mild cellular pleomorphism but had local invasion following local recurrence was also identified as an OC. Of the 11 cases with follow-up information, 7 cases had local recurrence. Regional or distant metastases were found in 6 and 4 cases, respectively. Five-year disease-specific survivals were 54.9%. In summary, OC of salivary gland origin is a high-grade tumor, often with local recurrence, regional or distant metastasis, diagnosis of which based on a combination of clinical and histopathological features. Immunohistochemistry for mitochondria is considered as a practical and helpful adjuvant diagnosis. Complete surgical excision is the treatment of choice while the role of radiotherapy or chemotherapy is controversial, and careful follow-up is necessary.