**4. Conclusions**

The work highlighted in this review clearly demonstrates a role for the tumor microenvironment in the growth, progression and metastatic invasion of cholangiocarcinoma. There is obviously a strong interplay between the cells found in the stroma and cholangiocarcinoma cells with signaling molecules passing back and forth between the cell types to co-ordinately support an environment that nurtures tumor growth and suppresses innate immunity while conferring resistance to cytotoxic insults (both endogenous and chemotherapeutic). The mechanism by which each of the support cells found in the stroma of cholangiocarcinoma tumors are recruited and activated is still largely unknown. Therapeutic strategies designed to target the microenvironment rather than specifically targeting the cholangiocarcinoma cells might prove fruitful in the quest to combat this devastating cancer.
