Proliferative activity of mixed hyperplastic adenomatous polyp/serrated adenoma in the large intestine, measured by PCNA (proliferating cell nuclear antigen).

The proliferative activity of serrated adenomas of the large intestine was determined by examining proliferating cell nuclear antigen (PCNA). The PCNA labeling index, determined by visual inspection, and the PCNA area rate, determined with the newly developed image processor for analytical pathology (IPAP), of serrated adenoma were found to be similar to the values for tubular adenoma, and indicated the presence of high proliferative activity in the bottoms of crypts. Determination of the pattern of distribution of PCNA-positive cells indicated the presence of a proliferative zone in the lower region or bottom of the serrated adenoma. However, 5 of the 20 serrated adenomas exhibited an irregular on widely extended proliferative zone, and 2 were complicated by cancer. These findings indicated that serrated adenoma is also a highly proliferative tumor and that it may be complicated by cancer if atypia is increased and disturbance of the proliferative zone is present.