Cholangiocarcinoma (CCA) is an aggressive neoplasia with an increasing incidence and mortality. It is characterized by a strong desmoplastic stroma surrounding cancer cells. Cancer-associated fibroblasts (CAFs) are the main cell type of CCA stroma and they have an important role in modulating cancer microenvironments. CAFs originate from multiple lines of cells and mainly consist of fibroblasts and alpha-smooth muscle actin (α-SMA) positive myofibroblast-like cells. The continuous cross-talking between CCA cells and desmoplastic stroma is permitted by CAF biochemical signals, which modulate a number of pathways. Stromal cell-derived factor-1 expression increases CAF recruitment to the tumor reactive stroma and influences apoptotic pathways. The Bcl-2 family protein enhances susceptibility to CAF apoptosis and PDGFRβ induces fibroblast migration and stimulates tumor lymphangiogenesis. Many factors related to CAFs may influence CCA prognosis. For instance, a better prognosis is associated with IL-33 expression and low stromal IL-6 (whose secretion is stimulated by microRNA). In contrast, a worst prognosis is given by the expression of PDGF-D, podoplanin, SDF-1, α-SMA high expression, and periostin. The maturity phenotype has a prognostic relevance too. New therapeutic strategies involving CAFs are currently under study. Promising results are obtained with anti-PlGF therapy, nintedanib (BIBF1120), navitoclax, IPI-926, resveratrol, and controlled hyperthermia.

Cholangiocarcinoma (CCA) is an extremely aggressive neoplasia, mostly because of diagnostic delay and lack of effective therapies. CCA is typically surrounded by a peculiar microenvironment that includes abundant desmoplastic stroma and various cell types, which support and enhance CCA development. Among the tumor microenvironment (TME) cells, there are tumor infiltrating lymphocytes (TILs), such as CD8+ and CD4+ cells, Tregs, natural killers (NKs) and B lymphocytes. TILs contribute to an immunosuppressive microenvironment that leads to tumor immune escape. Dendritic cells (DCs) may lead to immunotolerance by maturation or antigen-presentation deficiency. Hepatic stellate cells (HSCs) are one of the major precursors of cancer-associated fibroblast (CAFs), which are distinguished in various subpopulations, each with different functions and interactions with other TME cells. CAFs can promote lymphangiogenesis, early lymph-node metastasis and proinflammatory environment, but they can also provide a physical and chemical barrier to protect CCA. Tumor-associated macrophages (TAMs) could be differentiated between two phenotypes, pro- and anti-inflammatory, and they may sustain invasiveness and immunosuppression. Myeloid-derived suppressor cells (MDSCs) impair cytotoxic T lymphocytes (CTLs) function, stimulating tumor proliferation and angiogenesis. Tumor-associated neutrophils (TANs) function is influenced by the TME, leading to tumor-suppressing or tumor-promoting functions. This paper aims to provide an overview of the CCA microenvironment cells, their role in tumor progression and possible correlated diagnostic, therapeutic and prognostic implications.