The molecular mechanisms of platelets in tumor invasion and metastasis: a controversial role.

Platelets, traditionally recognized for their role in hemostasis, are now understood to actively contribute to tumor progression, angiogenesis, and metastasis. Through dynamic bidirectional interactions with cancer cells, platelets undergo measurable alterations in count, mean platelet volume, and molecular cargo, including proteins and mRNAs, supporting their potential utility as liquid biopsy biomarkers for early cancer detection. Within the tumor microenvironment, platelets contribute to immune evasion, support tumor cell intravasation and extravasation, enhance the survival of circulating tumor cells, and promote neovascularization. In addition, they can physically shield malignant cells from immune surveillance, thereby increasing metastatic potential. Although context-specific anti-tumor effects have been reported, the predominant evidence supports a largely pro-tumorigenic and pro-metastatic role for platelets. Elucidating the molecular mechanisms underlying platelet-tumor interactions is therefore essential for improving cancer risk stratification, prognostic evaluation, and therapeutic development. This review summarizes current advances in platelet-derived biomarkers and discusses emerging therapeutic strategies targeting platelet-mediated pathways to suppress metastasis and improve clinical outcomes in cancer patients.