WHO International Histological Classification of Tumours. Tentative Histological Classification of Salivary Gland Tumours.

The principles of the proposed modified WHO Histological Typing of Salivary Gland Tumours are based on the following: 1) The classification of tumours is oriented to the routine work of the practicing surgical pathologists, those who do not see tumours of the salivary glands very often. The inclusion of rare, but clearly defined tumour entities should be helpful to surgical pathologists consulting with clinical specialists. 2) The different types of carcinomas must be distinguished not only by precise histopathological definitions, but also considering differences in prognosis and treatment. For example, the polymorphous low-grade adenocarcinoma and the epithelial-myoepithelial carcinoma are characterized by a relatively good prognosis in contrast to the salivary duct carcinoma. 3) Special points of discussion are: subclassification and grading of carcinomas (e.g. acinic cell carcinoma, mucoepidermoid carcinoma and adenoid cystic carcinoma), the classification of basal cell tumours (basal cell adenoma, basal cell carcinoma, solid type of adenoid cystic carcinoma), malignant tumours in pleomorphic adenomas and the differential diagnosis between primary tumours and metastases.