Distribution of fibronectin and laminin in early and advanced signet‐ring‐cell carcinomas of the stomach

An immunoperoxidase method was used to compare the distribution of fibronectin and laminin between superficially spreading and deeply infiltrating parts of signet‐ring‐cell carcinoma of the stomach. In both parts, laminin‐containing basement membranes were generally scarce, but they were observed on some of the cancer cells which had differentiated to glandular cells. Intramucosal invasion fronts of superficially spreading cancers often showed a layered structure, consisting of a middle zone of small cancer cells together with a superficial and a deep zone of signet‐ring cells. In this structure, linear fibronectin and laminin deposits were common on the cancer cells in the deep zone, but rare in the superficial zone. However, fibrillar fibronectin deposits in the stroma were not considerably larger in either zone. At extramucosal invasion fronts of deeply infiltrating (advanced) cancers, a stromal remodelling with an increased amount of fibrillar fibronectin deposits was often observed around the cancer cells, whose cell surface fibronectin was largely lost even from some basement membranes. These findings suggest that invasive activity of signet‐ring‐cell carcinoma may not be related to the mere presence or absence of cell‐surface fibronectin and laminin but to the amount of stromal fibronectin, which could reflect a cell‐stroma interaction. Signet‐ring‐cell carcinomas have a stage of intramucosal growth in which cancer cells may live in dependence upon the pre‐existing stroma and form the layered structure, while in advanced stages cancer cells seemed to have acquired an ability to elicit their own “tumor stroma”.