A Multicellular Coordinated Network Driving Lymphovascular Space Invasion in Endometrioid Endometrial Carcinoma.

Lymphovascular space invasion (LVSI) is a critical factor linked to metastasis and poor outcomes in endometrioid endometrial carcinoma (EEC), yet its multicellular mechanisms remain unclear. Using single-cell RNA sequencing of 3 LVSI-present (LVSI+) EECs, 2 LVSI-absent (LVSI-) EECs, and 2 normal endometrial samples, we delineated the cellular ecosystems underlying LVSI. LVSI+ EECs exhibited marked epithelial reprogramming, transitioning from differentiated ciliated epithelium to hyperproliferative and metabolically remodelled phenotypes, and contained TC4, a metastatic epithelial subset characterized by hypoxia, partial epithelial-mesenchymal transition, immunosuppression, and progesterone resistance. We also identified nine key genes in malignant epithelial cells associated with LVSI prognosis. The tumour microenvironment in LVSI+ EECs shifted from an inflammatory state dominated by epithelial cells to a collaborative network involving stromal and immune cells. This network was enriched in immunosuppressive ZNF683 + SOX4 + CD8+ T cells, Cycling_T cells, SPP1 + MMP9 + Mac, WNT5A_mCAF, Tip endothelial cells, and lymphatic endothelial cells. WNT5A_mCAF and SPP1 + MMP9 + Mac synergistically remodelled the extracellular matrix, promoted lymphangiogenesis and angiogenesis, and, together with endothelial cells, suppressed T-cell activity via LGALS9-HAVCR2/CD44 inhibitory signalling, thereby establishing a niche conducive to vascular invasion. Using spatial multiplex immunofluorescence, we confirmed hypoxic tumour epithelial cells at the invasive front coexisting with an immunosuppressive microenvironment, and revealed spatial colocalization of PD-L1+ tumour cells, PD-L1+ macrophages, and PD-1+ T cells within LVSI thrombi. Our comprehensive study provides deeper insights into LVSI as an actively coordinated multicellular process, potentially improving LVSI risk prediction, supporting treatment decision-making, and informing new therapies targeting the tumour microenvironment.