[Research progress on perineural invasion and the immune microenvironment in biliary tract cancers].

Biliary tract cancer (BTC) is a group of highly malignant gastrointestinal tumors with poor prognosis, whose aggressiveness and therapeutic resistance are partly attributable to the complex interplay between perineural invasion (PNI) and the tumor microenvironment (TME). In recent years, accumulating evidence has shown that PNI not only promotes local tumor invasion and distant metastasis, but may also contribute to tumor immune evasion through modulation of the TME. This review summarizes the pathological features and molecular mechanisms of PNI in biliary tract tumors, including signal transduction between nerves and tumor cells, characteristics of the TME, intratumoral neural features, and alterations in immune cell function. In addition, the interactive mechanisms between PNI and the immune microenvironment are discussed, with a particular focus on the direct regulation of immune cells by neural signaling and the reciprocal effects of immune cells on PNI. Furthermore, this article reviews PNI-related prognostic models and therapeutic strategies, with the aim of providing new insights into precision diagnosis and treatment for BTC. By synthesizing current evidence, this review seeks to provide a theoretical basis for future investigations into the interplay between PNI and the immune microenvironment, as well as for the development of combinatorial therapeutic strategies.