Surgery based on misdiagnosis of adenomatous polyposis. The Canadian Polyposis Registry experience.

The histopathology of 304 patients registered in the Canadian Familial Polyposis Registry (CFPR) with a diagnosis of supposed adenomatous polyposis (AP) was reviewed. The diagnosis was changed in 17 (5.6 percent) of these patients. Group 1 consisted of nine patients who had adenocarcinomas plus multiple tubular adenomas (seven) or metaplastic polyps (two). Eight patients who had no colon cancer comprised Group 2. In these patients, the diagnosis was changed to lymphoid polyposis (2), metaplastic polyps (3), isolated adenomas (2), or juvenile polyposis (1). All 17 patients had had previous colonic resections. Following the change in diagnosis, this treatment was considered inappropriate in 11 patients. Treatment, prognosis, and follow-up of patients and affected family members depend on the type of polyposis syndrome diagnosed. Correct histologic assessment of polyps prior to initial surgery is essential.