Ultrastructural and Immunohistochemical Study of Salivary Duct Carcinoma of the Parotid Gland

A case of salivary duct carcinoma of the parotid gland found in an 81-year-old man was studied by light microscopy, immunohistochemistry, and electron microscopy. Histologically, the tumor was composed of elongated cords of cells and ductal structure with desmoplastic stromal reaction. Tumor cell nests sometimes showed central comedonecrosis. Immuno-histochemically, the tumor cells were positive for cytokeratin and epithelial membrane antigen, and they were negative for S-100 protein and muscle-specific actin. Electromicroscopi-cally, two cell types were identified. The first cell type showed electron-lucent cytoplasm with scant organelles. The second type cell contained numerous mitochondria. Neither acinar nor myoepithelial cell differentiation was observed. These findings suggest that salivary duct carcinoma originates from the interlobular or excretory ducts.     

Synchronous Benign Epithelial Tumors Arising in the Palatal Minor Salivary Gland: First Report of an Unusual Minor Salivary Gland Lesion

A review of the literature shows that unilateral benign salivary gland tumors of different histologic types in a single gland are so rare as to be curiosities, and all of such reported tumors have arisen in the parotid gland. The present paper reports a case of synchronous benign epithelial tumors of different histologic type arising in the palatal minor salivary gland of a 57 year old woman who had first noted palatal swelling about 20 years previously. Pathologically, the lesion was composed of two distinct tumors, pleomorphic adenoma and lumenless trabecular adenoma, which were sharply demarcated from each other by a thin layer of fibrous connective tissue. Foci of tumor cells with cellular atypia were seen in some areas of the pleomorphic adenoma. The present case is thought to represent a previously undescribed component within the spectrum of minor salivary gland tumors. Acta Pathol Jpn 40: 143–148, 1990.     

Tubular-Trabecular Type Basal Cell Adenoma of the Parotid Gland: A Patient Report

Basal cell adenoma (BCA) is an uncommon benign salivary gland neoplasm that includes isomorphic basaloid cells. We report on a female patient with BCA that developed in the right parotid gland in her 50s. The present patient demonstrated a few tumor nests in the fibrous capsule, and her tumor was larger than usual. These facts made us suspect of malignancy. Histopathologically, the tumor was characterized by multiple duct-like structures and tubular-trabecular masses composed of small isomorphic cells with hyperchromatic, round nuclei and an eosinophilic cytoplasm. It was difficult to determine whether the ductal structures noted in the tumor capsule were invasive. By immunohistochemistry, tumor cells of the tubular nests were positive for cytokeratin 7 and that the outer cells of tubular nests were positive for alpha smooth muscle actin (αSMA) and calponin. Tumor cells were immuno-negative for S-100 protein and glial fibrillary acidic protein. The Ki-67 labeling scores of the cells were extremely low (< 1%). We could achieve an accurate diagnosis of BCA by immunohistochemistry with MIB-1 and other markers.     

Neuroendocrine Differentiation in a Case of Acinic Cell Carcinoma of the Parotid Gland

We report a case of acinic cell carcinoma of the parotid gland with neuroendocrine differentiation. Light microscopically, the tumor appeared as clear cell-type acinic cell carcinoma. In addition, the tumor showed neurosecretory features such as Grimelius positivity and the presence of neurosecretory granules by electron microscopy. We suggest that a tumor cell arising from a stem cell can show simultaneous differentiation to both neuroendocrine and acinic cells.