metastasizing

Metastasizing, or metastasis, refers to the process by which cancer cells spread from a primary tumor to distant organs and tissues. Metastatic disease is a defining feature of malignant tumors, whereas benign tumors do not metastasize. Metastasis involves multiple steps: local invasion of surrounding tissue, entry (intravasation) into blood vessels or lymphatic channels, survival during circulation, exit (extravasation) into distant tissue, and colonization to form secondary tumors. The efficiency of this process is influenced by tumor cell properties, the microenvironment, and the interaction with the immune system. The "seed and soil" hypothesis describes how certain cancer cells ("seeds") colonize environments ("soil") that are favorable for growth, explaining site-specific patterns of metastasis.

Common metastatic sites vary by cancer type. Breast and prostate cancers often spread to bone; cancers of the lung, breast, and colon to liver; lung and breast cancers commonly metastasize to brain. Lymph node involvement is also common, especially in carcinomas that spread via the lymphatic system.

Detection typically involves imaging such as computed tomography (CT), magnetic resonance imaging (MRI), or positron emission tomography (PET), and may be confirmed by biopsy. Staging determines the extent of spread and guides treatment planning.

Treatment for metastatic cancer is usually systemic, aiming to control tumor growth and symptoms. Options include chemotherapy, targeted therapies, hormone therapy, immunotherapy, and supportive care; local treatments such as surgery or radiation may be used to relieve focal symptoms or complications. Prognosis depends on cancer type, extent of metastasis, and response to therapy.