Monoclonal antibody Adnab-9 defines a preneoplastic marker in epithelium at risk for adenocarcinoma of the small intestine

Unlike colorectal cancer, risk markers for adenocarcinoma of the small inte stine (ASI) have not been identified. Because the demographic and pathologi cal features of both of these diseases are similar, immunohistochemistry wa s performed using: monoclonal antibodies for three colonic premalignant mar kers, Adnab-9 (recognizes a colonic adenoma epitope), CaCo3/61, and FBB2/29 (small intestine proteoglycans expressed ectopically in colonic neoplasms) , in normal and neoplastic small intestinal epithelium, and the results wer e compared with normal controls. Adnab-9 was also examined in 20 familial a denomatous polyposis (FAP) patients, a population known to be at an increas ed risk for ASI. Immunohistochemistry in normal and neoplastic tissue (aden oma, adenocarcinoma) from 18 patients with primary adenocarcinoma of the sm all intestine was compared with normal small intestine from 10 nonneoplasti c controls. Four of 10 (40%) cases of normal small intestinal epithelium fr om controls were mildly positive in less than 10% of crypts, versus strong staining (>50% of crypts) in 16 of 18 (89%) patients with adenocarcinoma, a nd in 17 of 20 (85%) patients with FAP (P < .05). Adnab-9 predominantly sta ined Paneth cells as well as rare crypt and basal villous goblet cells. Ade nomatous epithelium from the adenocarcinoma cases and adenomas from the FAP patients showed staining of Adnab-9 in 63% and 78% of cases, respectively. Only 17% of adenocarcinomas were positive for Adnab-9. In contrast, neithe r CaCo3/61 nor FBB2/29 showed any significant differences in the degree of staining in normal small intestinal epithelium in patients with adenocarcin oma compared with controls. Enhanced Adnab-9 staining in normal small intes tinal epithelium from patients who harbor adenocarcinoma, and in FAP patien ts, supports its role as a risk marker of small intestinal neoplasia. Copyr ight (C) 1999 by W.B. Saunders Company.