Genetics of site specific colon cancer: a family study.

In a kindred of 46 individuals of an Indian Sikh family with no history of consanguinity, 8 suffered from site specific colon (caecum) cancer (not associated with polyposis). The clinical features in the affected kindred were indicative of a "cancer family syndrome". The study of the family depicted an autosomal dominant transmission pattern of site specific colon cancer, with probably 100% penetrance in the affected individuals. A low percentage of mitotic index (MI) was observed in the two probands who were available for the study. No structural or numerical chromosomal aberrations were observed in either case. It is probable that the gene responsible in this family could have begun by mutation at the germ cell level in the 1st generation and remained in a heterozygous condition in the affected individuals.