DNA content and proliferative activity of myoepitheliomas.

This report adds 16 myoepitheliomas of salivary glands to the 47 already recorded in the literature. It includes, for the first time, a flow cytometric analysis of their ploidy (DNA content) and proliferative capacity (S-phase fraction). Thirteen myoepitheliomas were diploid; three were aneuploid in their DNA content. A high proliferative capacity was always associated with an abnormal DNA content. Only one diploid myoepithelioma had a high S-phase fraction. Both flow-cytometric parameters are good predictors of an aggressive biological behaviour. Recurrences, however, were all the outcome of incomplete primary removal of the myoepitheliomas. Four of the twelve (33 per cent) diploid myoepitheliomas recurred and one, with high S-phase fraction, led to the death of the patient. Two of the three (67 per cent) aneuploid myoepitheliomas recurred. Extensive loco-regional invasion by one killed the patient. The other has clinical evidence of distant metastasis.