CD4 and invasive carcinoma: By evaluating total, stromal, and intraepithelial tumour-infiltrating CD3+, CD4+ and CD8+ T lymphocytes, CD20+ B lymphocytes, MUM1+ plasma cells, CD68+ macrophages, CD163+ M2-like macrophages and CD56+ NK cells in non-tumorous biliary tissue specimens, corresponding precursor lesions and invasive carcinoma samples of the same patients, we deciphered the distribution and spatiotemporal evolution of tumour-infiltrating immune cells during biliary carcinogenesis.