Flow cytometric DNA patterns from colorectal cancers--how reproducible are they?

The heterogeneity of DNA ploidy patterns within individual colorectal carcinomas was investigated by analyzing 261 different samples from 30 fresh colorectal cancers. The results of DNA analysis of multiple superficial cup biopsy specimens, of multiple full-thickness fresh tumor slices, and of nuclei extracted from paraffin-embedded pathologic archival specimens with use of the Hedley technique were compared. The same DNA ploidy pattern was found in all specimens of 19 (63%) of the 30 tumors studied. Minimal heterogeneity for DNA ploidy pattern was noted in seven carcinomas (23%), and moderate to marked heterogeneity was found in an additional four tumors (13%). The DNA pattern of a full-thickness specimen from 79% of the carcinomas studied was the same when samples were obtained from any one of five possible sites. In addition, the DNA ploidy pattern of the majority of the carcinomas could have been accurately predicted by flow cytometric DNA analysis of superficial cup biopsy specimens. These results demonstrate that most colorectal carcinomas are DNA ploidy homogeneous. Therefore, measurement of this tumor property can be used in future clinical research studies with some degree of confidence.