["Serrated" adenoma--a little known type of colorectal tumors].

: Eight cases and review of the literature on serrated adenoma of the colon were reported. This distinct entity of colorectal tumors was described in recent years. The tumors contain hyperplastic and adenomatous areas. Their tendency for malignant transformation is similar to pure adenomas to contrary to benign hyperplastic polyps. Three tumors of eight reported cases were pedunculated, while five were sessile. Four patients were operated on because of narrowing of intestinal lumen by the tumors. Malignant transformation of tumors was observed in three cases. Several biopsies were performed before major operations. Histology showed false benign hyperplastic tumors. Importance of multiple tissue sample for histology was emphasised. Electron microscopy showed disturbed differentiation and pathological mucus production of tumor cells.