This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: General Concepts, Subject name: Pathology
Which of the following is essential for tumor metastasis? 
Select and explain. 
A. Angiogenesis, B. Tumorogenesis, C. Apoptosis, D. Inhibition of tyrosine kinase activity
A: Angiogenesis
Answer: A: Angiogenesis 
Explanation: Metastasis is a complex series of steps in which cancer cells leave the original tumor site and migrate to other pas of the body the bloodstream or the lymphatic system. One of the critical events required for metastasis is the growth of a new network of blood vessels, called tumor angiogenesis.