Introduction
The molecular basis of metastasis is poorly understood. No single metastasis gene or specific genetic alteration that may be responsible for metastases has yet been identified. A recent paper (Chen T et al, Cancer Res 1999, 58:4805-4810) reported for the first time that mutations in the TGFβ receptor type I (RI) gene were associated with human cancer. Specifically, a C to A transversion at nucleotide 1160 of the gene, which would result in a serine to tyrosine substitution at codon 387 (S387Y), was described. In that study, 2 of 31 primary breast cancers and 5 of 12 lymph node metastases showed the mutation, leaving the authors to infer an association with metastatic progression.