Phospholipase activity in human tumors: localization by cytochemical staining.

Phospholipase activity was localized for the first time by cytochemical staining at the plasma membrane of malignant cells in gastric adenocarcinomas by electron microscopy. This activity was not found in benign cells of the same tumor, e.g., in components of the connective tissue underlying the glandular epithelium, or in cells beyond the margin of the same tumor. Neither benign nor malignant cells of colorectal tumors, nor those in malignant melanoma, had any phospholipase activity that could be demonstrated by the method.