Infrequent Replication Errors at Microsatellite Loci in Tumors of Patients with Multiple Primary Cancers of the Esophagus and Various Other Tissues

Patients with esophageal cancer are at high risk of developing other primary tumors, especially squamous cell carcinoma in the head and neck. Heavy smoking and excessive consumption of alcohol are considered to he crucial environmental risk‐factors for development of these multiple primary cancers. To investigate whether any genetic background, such as defects in the DNA‐mismatch repair system, may influence the development of these multiple primary tumors, we examined replication errors (RER) at six microsatellite loci in DNAs of 46 tumors from 33 patients who had developed primary cancers in various tissues in addition to the esophagus. RER(+) (RER‐positive) phenotype was observed in three tumors in two patients of the 33 patients examined. Our results suggested that development of multiple primary tumors in these patients would not be affected by an abnormality in the DNA repair system(s) detected as the RER phenotype. However, it is noteworthy that a single patient who developed multiple cancers revealed RER(+) phenotypes at multiple microsatellite loci in both tumors, indicating that a defect in the DNA repair gene(s) may have played an important role in the development of the tumors in this patient.