Mitmeaastases

Mitmeaastases, or metastases, are secondary malignant growths that arise when cancer cells spread from a primary tumor to distant organs or tissues. They are characteristic of malignant cancers and often determine prognosis and treatment strategy. Metastases may be detected at the same time as the primary tumor or develop during follow-up.

The spread process typically involves several steps: cancer cells invade surrounding tissue, intravasate into blood or lymphatic vessels, survive in circulation, extravasate into distant tissues, and establish new tumors. The "seed and soil" hypothesis describes how certain cancer cells (the seeds) preferentially colonize specific organ environments (the soil) that support growth. Genetic and microenvironmental factors influence metastatic potential and organ preference.

Common metastatic sites vary by cancer type. Hematogenous spread frequently targets the liver and lungs, while bone and brain metastases are also common in several cancers. Some cancers show limited dissemination, known as oligometastatic disease, which can be treated with targeted local therapies in addition to systemic treatment.

Diagnosis and staging rely on imaging modalities such as computed tomography, magnetic resonance imaging, and positron emission tomography, often complemented by biopsy to confirm histology. The presence and extent of metastases are incorporated into cancer staging systems (the M component of the TNM system), guiding treatment decisions. Molecular profiling and biomarkers may inform targeted therapies.

Treatment typically includes systemic therapies—chemotherapy, targeted therapy, immunotherapy, or hormonal therapy—depending on the cancer type and molecular characteristics. Local treatments such as surgery or radiotherapy can be used for selected metastases, aiming to control symptoms and, in some cases, improve survival. Prognosis varies widely with cancer type, number and location of metastases, and patient health.