What are the most common sites for metastasis of cancer cells?

The most common sites for metastasis of cancer cells are the brain, liver, lungs, and bones. This is due to various factors, including blood flow and the microenvironment of different tissues, which can influence where cancer cells spread.

The brain is a common site for metastasis because many cancers, particularly breast and lung cancer, can spread through the bloodstream or cerebrospinal fluid. The liver is often involved in metastasis due to its rich blood supply and role in filtering blood from the gastrointestinal tract, making it a prime target for cancer cells originating from abdominal cancers. The lungs serve as a key metastatic site because they receive venous blood from the entire body, providing a direct pathway for circulating tumor cells. Lastly, bones are frequently affected since some cancers release factors that promote their survival and growth within the bone microenvironment, leading to complications such as bone pain and fractures.

The other options include organs and tissues that are not typically associated with the most common metastatic spread of cancer, making them less relevant in the context of this question.