POSTN and cholangiocarcinoma: Intrahepatic CCA is mainly characterized by the presence of an abundant desmoplastic reaction, consisting of a dense, fibrotic, and infiltrating stroma enriched with collagen type 1 fibers, extracellular matrix (ECM) proteins such as periostin and tenascin C. The major cellular components of this desmoplastic stroma are CAFs, with inflammatory cells, such as tissue-associated macrophages (TAMs), tumor-associated neutrophils (TANs), regulatory T lymphocytes (Tregs), and natural killer cells (NK) [8,9].