The body is covered by a special drainage system called the lymphatic system. The lymphatic system is responsible for transporting excess fluid from the organs and tissues in a fluid called lymph.
Lymph fluid is transported through the lymphatic drainage system and passes through small nodules or nodes. These act as filters, filtering out unwanted substances.
Cancerous cells which break off from an organ that has cancer accumulated at the lymph nodes and infiltrate a different area of the body.