CD4 and neoplasm: Interestingly, ectopic MHC class II expression was observed on a number of human tumor cells, including breast cancer,17 carcinoma of the larynx,18 colon carcinoma,19 melanoma,20 and renal cell carcinoma.21 MHC class II expression in these cases may be a result of local secretion of inflammatory cytokines such as IFN-γ and TNF-α by tumor-infiltrating lymphocytes, as MHC-II expression was correlated with more intense CD4+ T-cell infiltration compared with MHC-II-negative tumors.