Sessile adenoma of the gallbladder. Reappraisal of its importance as a precancerous lesion.

Three hundred gallbladders from patients with cholelithiasis were examined under a dissection microscope. Sixteen (5%) were found to have what have been called sessile adenomas. They consisted of mixtures of hyperplastic lining epithelium and metaplastic mucous glands, and their interstitium often included smooth-muscle fibers. Small foci of moderately severe cellular atypism were present in 19% of the adenoma cases, but none had definitive evidence of malignancy. Carcinoembryonic antigen was demonstrated in hyperplastic lining epithelium with or without cellular atypism in 31% of the cases. Sessile adenomas most likely represent reactive overgrowth and therefore we prefer to term them hyperplastic polyps.