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

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.