Uterine carcinosarcoma associated with hereditary nonpolyposis colorectal cancer.

Background: Hereditary nonpolyposis colorectal cancer (HNPCC) was originally described as a genetic disorder predominantly involving colorectal cancer. Numerous neoplasms are known to be associated with this condition. Sarcomas have also been reported within families with HNPCC. The challenge is determining if these cancers are sporadic or hereditary.

Case: We report on a 46-year-old woman with uterine carcinosarcoma and a family history suspicious for HNPCC. Genetic testing identified a germline MLH1 mutation. Immunohistochemistry testing of the carcinosarcoma revealed loss of MLH1 expression with preservation of MSH2 expression.

Conclusion: The loss of MLH1 protein expression suggests the germline mutation contributed to the development of the carcinosarcoma. Hereditary nonpolyposis colorectal cancer should be included in the differential diagnosis of persons with uterine carcinosarcoma when noted within a family history suspicious for HNPCC.