Phenotypic variation in hereditary nonpolyposis colon cancer syndrome. Association with infiltrative fibromatosis (desmoid tumor).

Familial infiltrative fibromatosis (desmoid tumor) is a recognized complication of familial adenomatous polyposis (FAP) but has not been described in families without colonic polyposis. The authors describe a unique family in which a predisposition to infiltrative fibromatosis and nonpolyposis colon cancer was inherited dominantly through four generations. This report expands the range of phenotypic variation described for the hereditary nonpolyposis colon cancer (HNPCC) syndrome and adds to the extracolonic complications that are common with FAP and HNPCC.