Normal and abnormal mitoses in the atypical endometrial change associated with chorionic tissue effect [corrected].

The presence of mitotic figures was investigated in 215 cases of florid atypical endometrial change associated with chorionic tissue effect. Mitoses were found in 13.4% of the cases. Mitoses were occasionally observed in 10.2% of cases, and they were multiple in single microscopic fields in 2.7%. Abnormal mitoses were noted in 3.2% of the cases. The occurrence of normal and abnormal mitoses was mainly related to the early secretory type of abnormality. These observations have biologic implications, but of more practical interest, they indicate that the presence of mitoses per se are an insufficient criteria for the diagnosis of clear-cell carcinoma, particularly in women during their reproductive period.