metastasi

Metastasi, or metastasis, is the spread of cancer cells from a primary tumor to distant parts of the body, where they can form secondary tumors. It is a hallmark of malignant disease and a major factor in prognosis. Metastases most commonly affect the bones, liver, lungs, brain, and adrenal glands, but can involve virtually any organ. Not all cancers metastasize, and the pattern of spread depends on tumor type and biology.

The metastatic process involves multiple steps. Cancer cells invade surrounding tissue, enter blood vessels or lymphatic channels (intravasation), survive in circulation, exit vessels at distant sites (extravasation), and adapt to a new tissue environment to grow (colonization). The interaction between cancer cells and the target organ’s microenvironment, including immune and stromal cells, influences whether metastases establish. The “seed and soil” hypothesis is a classical concept describing why certain cancers preferentially colonize specific organs.

Diagnosis usually relies on imaging techniques such as computed tomography (CT), magnetic resonance imaging (MRI), and positron emission tomography (PET), complemented by biopsy to confirm histology. Staging uses systems like TNM to assess tumor size, nodal involvement, and distant metastases; distant spread is typically classified as stage IV in many cancers.

Treatment aims to control disease, relieve symptoms, and preserve quality of life. Approaches include systemic therapies (chemotherapy, targeted therapy, hormonal therapy, immunotherapy) and localized treatments (surgery, radiotherapy) directed at metastases when feasible. Prognosis varies widely by cancer type, extent and location of metastases, tumor biology, and patient factors.