Metastasis can occur primarily through which two circulatory methods?

Metastasis primarily occurs through the lymphatic system and the bloodstream, making lymph and blood the correct methods. Cancer cells can spread from the original tumor site to other areas of the body through these two systems.

The lymphatic system is a network of vessels that transport lymph, a fluid containing immune cells. When cancer cells enter these lymph vessels, they can travel to lymph nodes and subsequently to distant sites. This is particularly common in cancers such as breast and melanoma.

The bloodstream provides another route for metastasis. Cancer cells can invade blood vessels and circulate throughout the body. This method allows for the dissemination of cancer to vital organs such as the liver, lungs, or bones, which are common sites for secondary tumors.

Other options listed involve factors not related to the circulatory mechanisms used for metastasis in oncology. Air and water do not play a role in how cancer spreads, while cells and tissues refer more to the makeup of the body itself rather than mechanisms of metastasis. Saliva and bile are also not involved in the metastatic process. Thus, lymph and blood are indeed the primary methods through which metastasis occurs in oncology.