Final answer:
Cancer cells grow out of control and invade surrounding tissues during the metastasis stage, which often signifies an advanced and aggressive stage of cancer. Malignant tumors can spread to other parts of the body through the bloodstream, causing new tumors to form and complicating treatment considerably.
Step-by-step explanation:
The stage in the development of cancer when cancerous cells grow out of control, grow their own blood vessels, and invade surrounding tissues is known as metastasis. During the metastatic stage, cells from the primary tumor break away, enter the bloodstream or lymphatic system, and travel to other parts of the body. There, they can establish new tumors, interfering with the function of various organs. The spread of cancer through metastasis is a critical concern because it significantly complicates treatment and generally indicates an advanced stage of the disease with a poor prognosis
Malignant tumors are especially known for this invasive behavior as they have no limits to their growth, allowing them to damage neighboring tissues and spread throughout the body. This characteristic makes malignant tumors much more dangerous compared to benign tumors which remain localized and do not spread. The ability of cancer cells to form new blood vessels, a process called angiogenesis, further enables tumors to receive the oxygen and nutrients needed for continued growth and facilitates the invasion of adjacent tissues.