Invasion and Metastasis

Question 1

What are the hallmarks of malignant tumors?

Answer 1

Invasion and Metastasis; Usually through lymph and blood vessels or serosal surfaces.

Question 2

What are the most common sites of metastasis?

Answer 2

Lungs, bones, liver and brain.

Question 3

Describe the 7 steps of metastasis

Answer 3

1. Detach from primary mass
2. Invade local host tissue stroma
3. Penetrate lymph and blood vessels
4. Survive in circulation
5. Penetrate corresponding parenchyma
6. Survive in new environment
7. Divide to form new tumor

Question 4

Discuss tumor detachment from the primary mass

Answer 4

Degradation of ECM using proteases (MMPs, cathepsin D and urokinase plasminogen activator )

Question 5

Discuss cancer cell dissociation.

Answer 5

Changed cellular adhesions. Usually a loss of E-cadherin. There is also a epithelial to mesenchymal transition.

Question 6

Discuss cancer cell penetration into lymph and blood vessels.

Answer 6

Most cells die in the bloodstream. However, if not, they are coated with platelets and leukocytes creating a microembolus and adhere to activated endothelial cells.

Question 7

Discuss cancer cell survival in its new environment.

Answer 7

There must be an initiation of a viable premetastatic niche in the new organ.