Cancer researchers studying the conditions necessary for cancer metastasis have discovered that one of the critical events required is the growth of a new network of blood vessels, called tumor angiogenesis.
Several different cell types are critical to tumor growth.
The location of the metastases is not always random, with different types of cancer tending to spread to particular organs and tissues at a rate that is higher than expected by statistical chance alone.
Human cells exhibit three kinds of motion: collective motility, mesenchymal-type movement, and amoeboid movement.
The most common places for the metastases to occur are the lungs, liver, brain, and the bones.
This malignancy allows for invasion into the circulation, followed by invasion to a second site for tumorigenesis.
After the tumor cells come to rest at another site, they re-penetrate the vessel or walls and continue to multiply, eventually forming another clinically detectable tumor.
When tumor cells metastasize, the new tumor is called a secondary or metastatic tumor, and its cells are similar to those in the original or primary tumor.
Furthermore, ablation of the endothelial progenitor cells in the bone marrow can lead to a significant decrease in tumor growth and vasculature development.
Therefore, endothelial progenitor cells are very important in tumor biology and present novel therapeutic targets.
This means that if breast cancer metastasizes to the lungs, the secondary tumor is made up of abnormal breast cells, not of abnormal lung cells.