Which mechanism of metastasis involves the spread through the bloodstream?

The mechanism of metastasis that involves the spread through the bloodstream is hematogenous spread. This process occurs when cancer cells invade blood vessels and travel through the circulatory system, allowing them to reach distant organs and tissues. This form of metastasis is particularly common in certain types of cancers, such as those of the lung, liver, and kidney, and can lead to secondary tumors forming in various sites throughout the body.

In contrast, lymphatic spread refers to the dissemination of cancer cells through the lymphatic system, which is a network of vessels and nodes that help fight infection and remove waste. Seeding involves the spread of cancer cells to nearby organs and structures, often occurring in the abdominal or pelvic cavities. Direct invasion describes the extension of tumor cells into adjacent tissues without the intermediary of blood vessels or lymphatics. Understanding these different mechanisms allows for a better grasp of how tumors can metastasize and the implications for treatment and prognosis.