Patterns of GC invasion. (A, B) Washing pattern: cancer cells encroach extracllular matrix everywhere, like wave breaking the dike on the beach. (C) Ameba-like pattern: after breaking the collagen, cancer cells invade ECM along the interspace of collagen on both sides to form an Ameba-like ulcer. (D) Spindle pattern: cancer cells proliferate with polarity, and the collagen at the tumor-invasion front is hydrolyzed to overcome the ECM barrier, forming a potential invasive tunnel. (E, F) Linear pattern: cancer cells digest the ECM main along a line. (G, H) Type IV collagen was abruptly degraded at a point, several cells were migrating (G). Though type IV collagen was not broken, degradation was obvious. Magnifications: A: 200×, B-H: 400×. Red arrows present the trend of invasion. Black arrows indicate the breaking points of IV collagen by hydrolysis. All tissues were adenocarcinoma of GC.