CTM (Circulating Tumor Microenvironment)

The circulating tumor microenvironment (CTM) is the dynamic ecosystem of platelets, immune cells, and stromal components (such as cancer-associated fibroblasts) that circulating tumor cells actively interact with in the bloodstream.

Rather than passively drifting, CTCs cooperate with these components for physical shielding, paracrine signaling, and immune-checkpoint engagement — for example, platelet coating via P-selectin/PSGL-1 and CD155–TIGIT interactions helps CTCs evade immune detection.