Carcinoplacental alkaline phosphatase in malignant and premalignant conditions of the human digestive tract.

The presence of carcinoplacental alkaline phosphatase (CP Alk P) was demonstrated in the cells of malignant and premalignant states of the human stomach, colon and rectum using the immunoperoxidase technique. It was shown to be present in 7 out of 18 carcinomas of stomach and 7 of 17 cases of carcinoma of colon and rectum. In the putative premalignant states it was demonstrated in 4 of 15 cases of intestinal metaplasia associated with gastric carcinoma, and 9 of 12 tubulovillous adenomas of colon. However, it was also demonstrated in 5 of 8 metaplastic polyps of colon which are not neoplastic and in 9 of 17 cases of intestinal metaplasia not associated with cancer of the stomach. It was not seen in normal gastric mucosa and only faintly in 1 of 11 samples of normal colon. CP Alk P has been shown to be a specific marker of malignancy in a wide range of human cancers when studied in sera from patients or in tissue culture of tumour cells. In this study however, although a statistical difference exists between normal and diseased tissue the marker appears as frequently in non-neoplastic states. It is concluded that CP Alk P is, in tissues, a marker of proliferative activity in cells, rather than neoplastic or malignant change. In this respect it is similar in some respects to carcinoembryonic antigen, but not other markers of placental origin such as pregnancy specific beta, glycoprotein.