Selective Immunohistochemical Comparison of Polymorphous Low-Grade Adenocarcinoma and Adenoid Cystic Carcinoma

Aims



: The aims of this study were to ascertain the incidence of intercalated duct hyperplasia in association with cases of epithelial-myoepithelial carcinoma (EMC), and to explore a possible relationship between them and hybrid carcinomas of salivary glands.



Methods and results



: Seven cases of EMC with sufficient surrounding non-tumour parotid were examined. Three cases contained foci of intercalated duct hyperplasia adjacent to the tumour. One of the cases was a hybrid tumour composed of EMC and mucoepidermoid carcinoma. The hyperplastic intercalated ducts formed multiple foci within the salivary parenchyma and were composed of bland, uniform ducts. Cytological atypia was not identified.



Conclusions



: Intercalated duct hyperplasia may be a precursor lesion to EMC. Furthermore, it may also explain why EMC is frequently associated with other salivary gland carcinomas, so-called hybrid tumours, as well as sharing histological features with adenoid cystic carcinoma. Recognition of the latter is of particular importance because adenoid cystic carcinoma carries a poor prognosis.

Intercalated duct hyperplasia: possible relationship to epithelial-myoepithelial carcinoma and hybrid tumours of salivary gland.

Epithelial-myoepithelial carcinoma (EMC) of the salivary glands is an uncommon, low-grade malignant tumor. A recent report demonstrates sebaceous differentiation in this tumor even though its significance has never been documented as a precise histologic variant. Six cases of EMC exhibiting sebaceous differentiation (sebaceous EMC) of the parotid gland were analyzed for their clinicopathologic features and immunohistochemical characteristics. In addition, primary salivary sebaceous carcinomas were also examined for comparison. In our series, the incidence of sebaceous EMC was 0.2% among 3012 cases of parotid gland tumors and 14.3% of all EMC cases. The 6 patients comprised 2 men and 4 women, age ranging from 77 to 93 years (mean, 83.7 y). Neither cervical lymph node nor distant organ metastases were found in any cases of sebaceous EMC and no patients died of disease, though local recurrences developed in 1 patient. Conversely, cervical lymph node metastasis was detected in 2 of 3 patients with sebaceous carcinoma, 1 of whom died of disease at 12 months. Histologically, all 6 tumors had an area of sebaceous differentiation admixed with features of bilayered ductal structures typical of EMC. A component of sebaceous differentiation was distributed diffusely in 4 tumors and focally in 2. Cytologic atypia of sebaceous EMCs was lesser than that of sebaceous carcinomas. Immunohistochemically, putative myoepithelial markers such as alpha-smooth muscle actin, calponin, p63, cytokeratin 14, S-100 protein, and vimentin were highly expressed in sebaceous EMC. However, the expression of the latter 4 markers was also observed in primary sebaceous carcinomas, whereas these tumors were all negative for alpha-smooth muscle actin and calponin. Positive immunoreactivity for epithelial membrane antigen, adipophilin, and perilipin confirmed sebaceous differentiation in EMC. These results indicate that sebaceous EMC is a low-grade malignancy, similar to conventional EMC. Our data also suggest that immunohistochemical examination of specific myoepithelial markers is helpful in distinguishing sebaceous EMC from sebaceous carcinoma, which may occasionally be associated with an aggressive clinical course.

Sebaceous epithelial-myoepithelial carcinoma of the salivary gland: clinicopathologic and immunohistochemical analysis of 6 cases of a new histologic variant.

Salivary glands produce saliva. Saliva is secreted into the oral cavity by various large and multiple small glands.

Cancer of the Salivary Glands

Summary Epithelial-myoepithelial carcinomas (EMC) are rare neoplasms of the salivary gland with an incidence of less than 1% arising predominantly in the parotid gland. Although they are thought to be of low grade malignancy, fatal courses are described. We report a case of EMC of the parotid gland in a 58-year-old woman with an unfavorable course of this disease in long term follow-up. The malignant potential of this tumor is discussed. In addition, we include another case of EMC of the submandibular gland.

Epithelial-myoepithelial carcinoma of the salivary gland--a low grade malignant neoplasm? Report of two cases and review of the literature.

Epithelial-myoepithelial carcinoma (EMC) of the salivary glands is a rare tumor first described by Donath et al in 1972 and recognized as a distinct pathologic entity in the 1991 WHO classification. The EMC comprises approximately 1% of all salivary gland tumors. The histological hallmark is a biphasic cell arrangement formed by an inner layer of duct-forming epithelial cells and an outer layer of myoepithelial cells. The epithelial-myoepithelial dualism is confirmed using immunohistochemical methods: the epithelial cells are immunoreactive for low molecular weight keratin; the myoepithelial cells are immunoreactive for S-100 protein, muscle specific actin and vimentin. Most reported follow-up information indicates that EMC is a low-grade malignant tumor; however, from the analysis of the various series it is demonstrated that tumors with a solid growing pattern, nuclear atypia, DNA aneuploidy and high proliferative activity, generally have a more aggressive behavior and a higher frequency of local recurrences and metastases.

Epithelial-myoepithelial carcinoma of the salivary glands: a review of literature.

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Epithelial-myoepithelial carcinoma of the salivary glands: a review of literature.