Serrated adenoma of the duodenum.

The duodenum is the most common site for extracolonic adenomas in patients with familial adenomatous polyposis (FAP). These adenomas are usually tubular, villous, or tubulovillous. This report describes a patient with FAP who had a duodenal adenoma with a different histology--it had the microscopic attributes of a serrated adenoma--tumours that are relatively common in the colorectal mucosa and are occasionally found in the stomach. A 78 year old man with FAP and multiple adenomas was colectomised and the rectum amputated. Several years later he developed silent jaundice. The surgical specimen showed an adenomatous growth juxtaposing the papilla of Vater. The adenoma had epithelial fronds with crenated, sawtooth-like configurations caused by scalloped epithelial infolding. The nuclei covering the notched fronds were pleomorphic, stratified, either cigar shaped with irregular chromatin deposits or vesicular shaped with a large nucleolus. One area showed involvement of a duct by neoplastic epithelium with extension into periluminal glands. No invasive carcinoma was present. Serrated adenomas differ from tubular and villous adenomas in their histological organisation and their initial pattern of cell proliferation and genotypic aberration. Increased awareness of the existence of serrated neoplasms in the duodenum may result in similar cases being reported in the future.