The presence of oncofoetal antigens in large bowel carcinoma.

This paper is an immunohistological study of the occurrence of the oncofoetal antigens, (carcinoembryonic antigen (CEA), small intestine mucin antigen (SIMA), and normal large bowel mucin antigen (LIMA) in 60 surgically resected colons: 10 non-malignant specimens and 50 colorectal carcinomas. SIMA is a new oncofoetal antigen found in mucinous carcinoma of the large bowel. In the adult it is normally present only in the duodenum and jejunum. Of the 50 carcinoma specimens, 13 were mucinous, 17 non-mucinous and 20 mixed mucinous and non-mucinous. LIMA was the only antigen detected in the mucosa of non-malignant specimens. In mucinous carcinomas only SIMA was present, whilst in the non-mucinous specimens CEA was always found and to a lesser extent LIMA. The same relationship was observed in mixed tumours: SIMA in mucinous and CEA-LIMA in the non-mucinous parts. In the mucosa adjacent to the cancer in all 50 cases there was evidence of an increase or decrease in LIMA. In 42 cases (84%) both oncofoetal antigens (CEA and SIMA) could also be detected in this transitional or perineoplastic epithelium at varying distances from the tumour. These results provide evidence to suggest that the majority of large bowel carcinomas occur in areas of metaplastic change.