Published: 18 Jun 2025

ICD9: 198.89      ICD10: C79.9      ICD11: MG30.10

Metastasis is the spread of cancer cells from the place where they first formed to another part of the body.
It's a complex, multi-step process, and it's what makes cancer so dangerous and difficult to treat.

Here's a breakdown of the key aspects:

Original (Primary) Tumor: This is the initial site where the cancer cells originated.

Detachment and Invasion: Cancer cells need to break away from the primary tumor and invade surrounding tissues.

Entering the Circulation: These cells enter the bloodstream or lymphatic system, allowing them to travel to distant sites. This is like cancer hitching a ride.

Survival in Circulation: The cells must survive the harsh environment of the blood or lymph, evading the immune system and physical stresses.

Extravasation: Cancer cells need to exit the bloodstream or lymphatic system at a new location.

Colonization and Growth: Finally, the cells must settle in the new location, establish a new blood supply (angiogenesis), and grow into a new, secondary tumor. This secondary tumor is called a metastasis.

Why is Metastasis Important?

Increased Mortality: Metastatic cancer is much more difficult to treat than cancer that is confined to the primary site. The majority of cancer deaths are due to metastasis.

Treatment Challenges: Metastatic cancer often involves multiple sites, making surgery or localized radiation therapy less effective. Systemic treatments like chemotherapy and targeted therapies are used, but they may not always be successful.

Staging of Cancer: The presence and extent of metastasis are major factors in determining the stage of cancer, which helps guide treatment decisions and predict prognosis.

Key Factors Involved in Metastasis:

Genetic Mutations: Accumulation of genetic mutations in cancer cells can give them the ability to metastasize.
Tumor Microenvironment: The environment surrounding the tumor plays a crucial role. Interactions between cancer cells and surrounding tissues, immune cells, and blood vessels can promote or inhibit metastasis.
Epithelial-Mesenchymal Transition (EMT): This is a process where cancer cells lose their cell-to-cell adhesion and gain migratory and invasive properties.

Example:

If breast cancer cells spread to the lung, the cancer in the lung is not lung cancer. It's metastatic breast cancer. The cells in the lung are still breast cancer cells, and they are treated as such.

In summary, metastasis is the spread of cancer from its primary site to other parts of the body, and it is the primary reason why cancer is such a deadly disease. Understanding the mechanisms of metastasis is crucial for developing more effective cancer treatments and improving patient outcomes.