Invasion (cancer)

Invasion is the process by which cancer cells directly extend and penetrate into neighboring tissues in cancer.^[1] It is generally distinguished from metastasis, which is the spread of cancer cells through the circulatory system or the lymphatic system to more distant locations. Yet, lymphovascular invasion is generally the first step of metastasis.

There exist two main patterns of cancer cell invasion by cell migration: collective cell migration and individual cell migration, by which tumor cells overcome barriers of the extracellular matrix and spread into surrounding tissues. Each pattern of cell migration exhibits distinct morphological features and is governed by specific biochemical and molecular genetic mechanisms.

Two types of migrating tumor cells, mesenchymal (fibroblast-like) and amoeboid, can be observed in various patterns of cancer cell invasion. This article describes the key differences between the variants of cancer cell migration, the role of epithelial-mesenchymal and related transitions, as well as the significance of different tumor factors and stromal molecules in tumor invasion. Morphological manifestations of the invasion patterns are characterized by a variety of tissue (tumor) structures.^[2]