Systematic evaluation of the World Health Organization classification of salivary gland tumors. A clinicopathologic study of 366 cases

In an evaluation of the WHO classification of salivary gland tumors, 339 major and 27 minor salivary gland tumors were examined, these being all seen during the yr 1948-1968. The clinical records were examined and follow up data (average 8.7 yr) were obtained in 88% of cases. The relative incidences of sites and tumor types were similar to those in previously reported series. The WHO classification was found to be applicable to this group of tumors with the following exceptions: cases of chronic sialadenitis, and lymphomas presenting primarily as salivary gland masses (4.1% of all cases in this series), do not appear in this classification but frequently present problems to the pathologist and ought to be included in any subsequent revision; the histologic concept of 'differentiation' was not helpful in predicting the outcome of cases of mucoepidermoid tumor and acinic cell tumor; some confusion, possibly justified, still exists between poorly differentiated acinic cell tumors and adenocarcinomas; and a high frequency of atypical histologic types was encountered among the minor salivary gland tumors, suggesting that this group might benefit from separate treatment. Adequate surgical excision played a decisive role in the eventual result. In conclusion, the WHO classification of salivary gland tumors proved to be a practical guide for the categorization of the vast majority of this group of lesions.