Cancers commonly metastasize to which organs?

• A. Heart, kidneys, spleen, and skin
• B. Muscle, fat, cartilage, and tendon
• C. Stomach, intestines, pancreas, and bladder
• D. Lung, liver, bone, and brain

Answer: (D)

Metastasis spreads through blood and lymphatic routes, so the organs that routinely become sites of secondary tumors are those with high blood flow and receptive microenvironments. The lungs often capture circulating tumor cells from many parts of the body, making them a common first stop for metastasis. The liver receives blood from the portal and systemic circulation, providing another rich habitat for tumor cells to lodge and grow. Bones offer a dense network of blood vessels and a bone marrow–rich niche that many cancers exploit, and the brain presents a unique vascular and microenvironment that some tumor cells adapt to for growth.

Because of these factors, the combination of lung, liver, bone, and brain stands out as the most frequent metastasis targets across many cancer types. Other listed sites tend to be less commonly involved overall, either because they’re less conducive to tumor growth in the metastatic setting or because they’re less frequently reached by circulating cancer cells.