Invasion and Metastasis
Educational orientation
Source-checked: 2026-06-05. This page is conceptual and does not estimate individual risk.
Core Idea
Invasion means cancer cells have moved into nearby tissue. Metastasis means cells from the original cancer have established disease elsewhere. A metastatic tumor is usually named after the original cancer, not the organ where it is found.
Metastasis is a biological process with many steps: local invasion, entry into blood or lymph, survival during travel, exit into another tissue, and growth in that new environment.
Essential Vocabulary
- Local invasion: spread into nearby structures.
- Lymph node: immune structure that can contain cancer cells.
- Distant metastasis: disease in a far site.
- Primary site: where the cancer started.
What This Does Not Mean
Finding disease in another organ does not automatically mean that organ's usual cancer type. Tissue origin and pathology matter.
Builder/Data Lens
Datasets should distinguish primary site, metastatic site, specimen site, and diagnosis label. Mixing them creates serious errors.
Go Deeper
References
- National Cancer Institute. What Is Cancer?
- National Cancer Institute. Cancer Staging