Pedunculated oncocytic carcinoma in buccal mucosa: immunohistochemical and ultrastructural studies

In this study we evaluated pedunculated oncocytic carcinoma (OC) in the buccal mucosa via immunohistochemical and ultrastructural studies.

An 84-year-old man was referred to our clinic with a pedunculated mass about 4 cm in diameter in the right buccal mucosa. An incision biopsy revealed the diagnosis of oncocytic tumor, and enucleation was performed. The tumor was stained for immunohistochemical analysis using the ABC method and antibodies against cytokeratin (CK), epithelial membrane antigen (EMA), desmin, S-100 protein and muscle-specific actin, respectively. The tumor was stained with uranyl acetate and lead citrate for visualization by electron microscopy.

Histopathology results revealed that the tumor consisted of oncocytic cells, characterized by eosinophilic and granular cytoplasm, and atypical nuclei. These cells had infiltrated local blood vessels, salivary glands and muscles. Immunohistochemical staining indicated that these cells were positive for CK and EMA, and negative for desmin, muscle-specific actin and S-100 protein. Electron microscopy revealed numerous dilated cytoplasmic mitochondria, and the cell contours and nucleic shapes of tumor cells were often irregular.

Because the histopathologic features of OC are similar to those of benign oncocytoma, the diagnosis of OC must be confirmed by a combination of clinical and ultrastructural characteristics.