IL22 and neoplasm: As shown in Fig. 3G, tumor cells appeared pleomorphic with no sign of basement membrane and disappearance of acinar structures in tumors from recIL‐22‐injected IL‐22−/−/PyMT mice, whereas in control IL‐22−/−/PyMT mice, tumors appeared to be confined by basement membrane with florid epithelial cell proliferation, which characteristically represents adenoma/MIN stage of tumor progression.