Spread of Cancer

Cancer spreads in the body by local invasion and by metastases. Cancer (malignant tumour) usually grows in size by progressive infiltration and invasion, destroying the adjoining tissues. Although cancer can invade any tissue in the body, connective tissue is the softest target. After the initial growth, some of the cancerous cells become free from the primary tumour. These cells penetrate the blood vessels, lymphatic channels & body cavities and travel through the respective channels to lodge themselves in different tissues and organs of the body. These migrated cancerous (malignant) cells continue to grow at their new locations, forming secondary growths known as metastases. Most of the carcinomas metastasise through the lymphatic channels. In lymphatic spread, first of all, the local lymph nodes are involved, after which the cancerous cells travel through the natural route of lymphatic drainage. Sometimes the local lymph nodes are bypassed (Skip metastasis). Most of the sarcomas metastasise through the bloodstream usually to the lungs, liver and bones. The third common way of metastases is by implantation or seeding in body cavities, usually in the peritoneal cavity. Seeding can occur in the skin or mucous membrane having close contact with the primary cancer. Sometimes, seeding of cancer is seen in post surgery wounds. Some cancers such as renal cell carcinoma have the propensity to invade veins and grow in a snake like fashion upwards in the inferior vena cava, reaching up to the heart.