Metastasis

Metastasis is the process by which cancer cells spread from their original (primary) location to other parts of the body, forming secondary tumors in new organs or tissues. It marks a more advanced and dangerous stage of cancer, often making it harder to treat.

🔑 Definition:

Metastasis is the spread of malignant cells from a primary tumor to distant sites in the body through the bloodstream, lymphatic system, or direct invasion, resulting in the formation of secondary tumors.

🧪 How Metastasis Happens: Step-by-Step

1. Local Invasion
   Cancer cells invade neighboring tissues around the primary tumor by breaking through the basement membrane.
2. Intravasation
   Cells enter nearby blood vessels or lymphatic vessels, gaining access to circulation.
3. Circulation
   Tumor cells travel through the bloodstream or lymphatic system, surviving physical stress and immune attack.
4. Extravasation
   Cells exit the circulation at distant sites by adhering to vessel walls and penetrating into new tissue.
5. Colonization
   The cancer cells settle, survive, and multiply in the new tissue, forming a secondary tumor.

🧠 Not all circulating tumor cells succeed in forming new tumors. Metastasis is highly inefficient, but when it occurs, it’s clinically serious.

🔬 Common Sites of Metastasis:

⚠️ Why Metastasis Is Dangerous:

• It often means cancer is in an advanced stage.
• Metastatic tumors are harder to surgically remove.
• The new tumors may resist standard treatments.
• It can disrupt vital organ function depending on the site affected.

🧠 Key Biological Traits That Support Metastasis:

📌 Summary:

Metastasis is the hallmark of malignant cancer. It involves cancer cells leaving their original site, traveling through the body, and forming tumors in new locations. This process makes the disease more life-threatening, and managing metastasis is a major challenge in oncology.