Molecular Mechanisms Underlying Lymphovascular Invasion in Invasive Breast Cancer

Lymphovascular invasion (LVI), the presence of malignant cells within lymphovascular channels, is a crucial step in the invasion-metastasis cascade. LVI, when identified morphologically in the peritumoural area, is regarded as an indicator of metastatic potential and is strongly associated with a poor prognosis in many solid tumours, including breast cancer (BC). Although molecular mechanisms associated with the development of LVI have been extensively studied, details of driver genes, and molecular pathways and mechanisms involved in its development in BC, remain poorly defined. Although invasive BC cells have the ability to invade surrounding stroma, only those that can interact with endothelial cells, penetrate the vascular wall and withstand the intravascular stress will develop LVI and complete metastatic dissemination. Identification of additional molecular events associated with LVI in the primary tumour and characterisation of the contribution of the tumour micro-environment to modulating biological processes leading to LVI in BC remain a challenging task. This stems not only from the complexity of the molecular alterations in the primary tumour and the interactions with different components of its micro-environment but also from the subjective nature of LVI assessment in human BC. In this review, we discuss the clinicopathological features and the current knowledge of the molecular mechanisms underlying LVI in BC.