Rectal cancer in a 13-year-old boy without a detectable germline mutation in FAP and HNPCC genes.

Hereditary non-polyposis colorectal cancer (HNPCC) is characterized by familial clustering and early onset. It is unclear, however, whether the early onset of colorectal cancer necessarily represents HNPCC. A 13-year-old patient had rectal cancer and underwent curative surgery. DNA from this patient was examined for replication errors (RER) and genes related to familial colorectal cancer (APC, hMSH2, and hMLH1). The patient had a negative family history of colorectal cancer, did not show the RER phenotype, and had no germline mutation of the APC, hMSH2, and hMLH1 genes. The present case suggests that an unusually young patient with colorectal cancer is not always an HNPCC proband. Observation over time, however, will be needed, as a first mutator of familial colorectal cancer could be missed.