Microsatellite instability in endometrial carcinomas: clinicopathologic correlations in a series of 42 cases

Instability at microsatellite repeat sequences (MI) has been observed in endometrial carcinomas (EC) arising sporadically or in association with the hereditary colon cancer syndrome. However, the clinical and pathological features of the EC with MI have not been characterized. DNA of 42 patients with EC was extracted from blood and from fresh-frozen and paraffin-embedded tumor tissue. Microsatellite loci on chromosomes 4, 5, 10, 12, 17, and 18 were amplified by polymerase chain reaction. MI was defined by a mobility shift in the tumor DNA as compared with normal DNA. Results were correlated with the clinical and pathological features of the tumors. MI at three or more loci was detected in 12 of 42 cases (28%). There were no significant differences between EC with and without MI with regard to age of presentation, stage, evidence of estrogenic stimulation, mucinous differentiation, estrogen receptor, c-erbB2, or p53 immunostaining. However, MI was more frequent in endometrioid (11/33, 33.3%) than in nonendometrioid (1/9, 11%) carcinomas. Only one papillary serous carcinomas showed MI. MI was found in one of two cases of endometrial hyperplasia adjacent to EC. It was concluded that MI is a common genetic abnormality of endometrial carcinoma and appears to be more frequent in endometrioid than in nonendometrioid tumors.