Origin of multiple "primary" colon carcinomas. A retrospective flow cytometric study.

Multiple, synchronous, apparently primary carcinomas of the colon are a relatively common occurrence. The DNA ploidy in 23 colon carcinomas from 10 patients was determined to see if this parameter supported common or independent origins for such synchronous lesions. Paraffin blocks of each tumor were prepared for flow cytometry, then analyzed for nuclear DNA content. In 3 of the 10 cases, the tumors within each colon differed with respect to DNA ploidy; in four cases all tumors were diploid; and in three cases both (all) tumors within each colon had identical aneuploid DNA indices. Tumors from the same colon with identical DNA histograms often had dissimilar histology. The replicate aneuploid DNA indices strongly suggest a common origin for the multiple tumors within these colons; tumors in the other groups are compatible with either single or multiple origins. These findings suggest that multiple "primary" colon carcinomas may, in some cases, arise as translumenal metastases from an initial single lesion.