Incidence of microsatellite instability in synchronous tumors of the ovary and endometrium.

PURPOSE Families with hereditary nonpolyposis colorectal cancer (HNPCC) have an increased lifetime risk of endometrial (40%) and ovarian (10%) carcinomas. Endometrial and ovarian carcinomas from members of these families frequently display a mutator phenotype as manifest by high levels of microsatellite instability (MSI-H). Microsatellite instability (MSI) occurs in 17-32% of sporadic endometrial carcinomas and 3-17% of sporadic ovarian carcinomas. We hypothesized that there might be a higher rate of MSI in tumors from women with synchronous primary carcinomas of the ovary and endometrium. EXPERIMENTAL DESIGN We identified 52 cases of synchronous tumors of the ovary and endometrium from the databases of four gynecological oncology units. Archival material and clinical data were available on 45 of these patients. We examined DNA extracted from ovarian and endometrial tumor tissue for MSI using DNA extracted from normal tissue of that patient as a germ-line DNA control. MSI was assessed using a panel of five standard microsatellite markers: D2S123, D5S346, D17S250, BAT25, and BAT26. MSI-H was defined by more than two markers being positive. Low-level MSI (MSI-L) was defined as one or two markers positive and microsatellite stable (MSS) was defined as no markers positive. RESULTS The 45 patients had a median age at diagnosis of 53 years. Of a total of 134 samples analyzed, only three samples (3.3%) were MSI-H. No patient had high levels of MSI in both ovarian and endometrial tumors. One ovarian carcinoma had five of five markers positive with the corresponding endometrial carcinoma being MSI-L. Two endometrial carcinomas were MSI-H, and the corresponding ovarian carcinomas were MSI-L and MSS, respectively. Seven ovarian tumors and seven endometrial tumors were MSI-L. The majority of patients had early-stage ovarian carcinoma [International Federation of Gynecology and Obstetrics (FIGO) stage I, 44.4%; stage II, 26.7%; and stage III, 26.6%]. Eighty-two % of the endometrial primaries were FIGO stage I. Progression-free survival was significantly better for patients with synchronous primaries than those presenting with ovarian carcinoma alone [adjusted hazards ratio, 1.94; P = 0.023; 95% confidence interval, 1.096-3.44]. CONCLUSION Synchronous primary carcinomas of the ovary and endometrium are unlikely to be part of the HNPCC syndrome unless the family history is in keeping with the modified Amsterdam criteria.