metastasise

Metastasise is the process by which cancer cells spread from a primary tumor to distant sites in the body, forming secondary tumors called metastases. It is distinct from local invasion at the original site.

Metastasis involves a sequence of steps: invasion of adjacent tissue, entry into blood or lymphatic vessels (intravasation), survival in circulation, exit at distant sites (extravasation), and colonization of new tissue. Dissemination can occur early or later in cancer development, and the pattern of spread reflects tumor biology and organ microenvironments.

Biological traits such as increased motility, resistance to cell death, and epithelial-to-mesenchymal transition contribute to metastatic potential. The interaction of cancer cells with distant tissue stroma, immune cells, and blood vessels shapes site preference, a concept known as organotropism or seed-and-soil theory. Common targets vary by cancer type.

Clinically, metastasis usually signals advanced disease and affects prognosis. Treatments emphasize systemic therapies—chemotherapy, targeted therapies, and immunotherapy—that reach cancer cells throughout the body. Local treatments such as surgery or radiotherapy may control individual metastases or relieve symptoms; occasionally, limited metastases are removed to extend survival.

Diagnosis relies on imaging (CT, MRI, PET) and biopsy to confirm metastases and identify the tissue of origin. Monitoring may use tumor markers or repeat imaging to assess response.