What does "invasion" refer to in the context of cancer?

In the context of cancer, "invasion" refers specifically to the process by which cancer cells spread into and disrupt nearby tissues. This characteristic is a defining feature of malignant tumors, which are known for their ability to invade surrounding healthy tissues. Unlike benign tumors, which remain localized and are usually encased in a capsule, invasive cancers extend beyond their original boundaries and can invade adjacent organs and structures.

This is an important aspect of cancer progression, as the ability to invade surrounding tissues can lead to more advanced stages of cancer and contribute to metastasis, where cancer cells can spread to distant sites in the body. Understanding invasion is crucial for assessing the aggressiveness of a tumor and determining appropriate treatment options.