Pathogenetic implications of DNA nondiploidy in colorectal cancers

PURPOSE: Several studies propose that proximal and distal colorectal cancers have a different pathogenesis. We tested the hypothesis using flow cytometric DNA analysis. METHODS: DNA analysis was performed in 719 patients with colorectal cancer. In addition, histopathologic data were re-evaluated in a blinded fashion by a single pathologist. RESULTS: Distal tumors were more often nondiploid than were proximal tumors (61 vs. 49 percent; P = 0.015). Compared with the proximal tumor, distal tumors were smaller (P = 0.0001) and had less desmoplastic reaction (39 vs. 53 percent; P = 0.0001). Tumor location had no significant associations with the remaining parameters, including mucin production, perineural invasion, blood/lymphatic vessel invasion, lymphocytic infiltration, histologic grade, tumor stage, gross appearance, age, and gender. CONCLUSIONS: The unequal distribution of ploidy suggests distinct pathogenetic mechanisms at proximal and distal sites.