High risk of endometrial cancer in colorectal cancer kindred is pathognomonic for MMR-mutation carriers.

Endometrial cancer is frequent in MMR-mutation carriers. Estimates of annual incidence rates have, however, been based on retrospective studies. The purpose of our study was to prospectively assess the incidence rates of endometrial cancer in women either having a mutation in one of the four MMR genes MLH1, MSH2, MSH6 or PMS2 (Mut+) or belonging to families meeting the revised Amsterdam criteria in which no MMR mutation was detected (Ams+). Eight out of 80 Mut+ (10%) contracted invasive endometrial cancer compared to 1/171 (0.6%) of the Ams+ (P = 0.0006). The annual incidence rate after first control was 2.5% in Mut+ and 0.2% in Ams+. Two of the 8 Mut+ women (25%) had synchronous gynaecological tumours. The numbers included did not allow for firm conclusions, but the results are in keeping with the notion that the inherited colon-endometrial cancer syndrome may be restricted to carriers of MMR mutations.