CD8A and neoplasm: To our surprise, although metastasis was not observed in 4MOSC1 control mice (see above), the cervical lymph nodes of CD8-depleted mice with 4MOSC1 tumors showed tumor invasion, as indicated by cytokeratin 5 staining (Fig. 3f) and visualization with H&E staining (Supplementary Fig. 7c) suggesting that immune surveillance may prevent the metastatic spread of this tumor.