Metastasize

Metastasize refers to the process by which cancer cells spread from a primary tumor to distant organs or tissues, forming secondary tumors called metastases. Metastasis is a defining feature of malignant cancers and is a major determinant of prognosis and treatment strategy.

The metastatic cascade involves several steps. Cancer cells must detach from the original mass and invade surrounding tissues, then penetrate into blood vessels or lymphatic channels (intravasation). They must survive the hostile conditions of circulation, arrest at distant sites, exit vessels (extravasation), and adapt to a new tissue environment to grow (colonization). Molecular changes in cancer cells, interactions with surrounding stromal and immune cells, and the creation of a supportive microenvironment all contribute. Theories such as the epithelial‑to‑mesenchymal transition and the “seed and soil” hypothesis help explain how cells acquire invasive potential and why certain tumors preferentially colonize specific organs.

There are several routes of spread. Hematogenous spread carries cancer cells through the bloodstream to organs such as the liver, lungs, and brain; lymphatic spread leads to regional and distant lymph nodes; transcoelomic dissemination can spread across body cavity surfaces. Common metastatic sites vary by primary tumor type; for example, colorectal cancers frequently involve the liver, breast cancers often spread to bone, liver, lung, and brain, and prostate cancers commonly metastasize to bone.

Detection relies on imaging and histopathology to confirm metastases and distinguish them from the primary tumor. Treatment typically emphasizes systemic therapies (chemotherapy, targeted therapy, immunotherapy) while local approaches may be used for a limited number of metastatic lesions in selected cases. Metastasis status is a key component of cancer staging and prognosis.