Wijnen et al. (1999) found that atypical HNPCC families with MSH6 mutations displayed a very high frequency of atypical hyperplastic lesions and carcinomas of the endometrium: 73% in female MSH6 mutation carriers compared with 29% in MSH2 and ... Wijnen et al. (1999) found that atypical HNPCC families with MSH6 mutations displayed a very high frequency of atypical hyperplastic lesions and carcinomas of the endometrium: 73% in female MSH6 mutation carriers compared with 29% in MSH2 and 31% in MLH1 carriers. Moreover, delayed age of cancer onset and incomplete penetrance were characteristic clinical features of the MSH6 mutation carriers. The results indicated that tumors of the endometrium (608089) represent the most common clinical manifestation of HNPCC among female MSH6 mutation carriers and that colorectal cancer cannot be considered an obligatory requisite to define HNPCC. Wagner et al. (2001) found that colorectal cancer was significantly decreased in a large Dutch family with atypical HNPCC and an MSH6 mutation compared to families with mutations in MSH2 (609309) or MLH1 (120436) (p less than 0.001). Endometrial cancer was frequent among female mutation carriers (6 of 13 malignant tumors), and transitional cell carcinoma of the urinary tract was present in 10% of male and female carriers. The mean age of onset of colorectal and endometrial cancer was delayed compared to that in families with MSH2 or MLH1 mutations. Suchy et al. (2002) described a Polish MSH6 family in which a late-onset endometrial type of ovarian cancer was a feature. In the proband, bilateral ovarian cancer was discovered at the age of 49 years. The father died of colon cancer at the age of 83 years and her paternal grandmother died of endometrial cancer at the age of 69 years. Endometrial cancer was diagnosed at the age of 57 years in a cousin. Ovarian cancer had been reported in an MSH6 family by Wagner et al. (2001).