Electron Microscopic Studies on Mucoepidermoid Carcinoma III.On the ultrastructural atypy

Using disected materials from two cases of mucoepidermoid carcinoma, the ultrastructural appearances of tumor cells were studied. Ultrastructural atypy of the nuclei and the cytoplasms appeared in both cases of tumor cells. It was considered that the existance of ultrastructural atypy proved this neoplasm to be a true malignant tumor. Based upon the above mentioned results, the biological behavior of this neoplasm was discussed. It was determined that the name of this neoplasm was mucoepidermoid carcinoma, and was classified into two groups : the well-differentiated (low-malignant) type and the undifferentiated (high-malignant) type