On the other hand, some tumors grow far more rapidly and often lose all similarity to the cells from which they started. The cells of these tumors tend to invade surrounding tissue and destroy healthy cells. They lose the normal capacity of cells to stick together. Individual cells can break away from the tumor and be carried in the blood stream or lymphatics, to distant parts of the body where they implant and begin growing just like the original tumor. Tumors of this type are called malignant and they make up the group of disorders known as cancer. Some tumors begin as benign and then turn malignant after a period of benign growth. This pattern is known as precancerous. Early in their development, cancers may not appear to do any harm. As the primary lesion begins to invade surrounding tissue, cell damage occurs. Wherever a secondary lesion develops, tissue is destroyed and impairs the function of the host organ. Eventually, a malignant growth may erode through major or minor blood vessels, resulting hemorrhages. These changes may bring pain, progressive loss of normal body functions and ultimately death. Even in the absence of such symptoms, cancer has other widespread and generalized debilitative effects. Many times the body may become toxic with a persisting fever. Symptoms such as nausea, vomiting or loss of appetite may occur. Weight loss is common. It is difficult to eat, and fatigue is prevalent.
Warning signs include persistent hoarseness, difficulty in swallowing, lump in the breast or discharge from a nipple, persistent cough, any abnormal bleeding, any changes in a mole or pigmented area on the skin, unexplained fever, unexplained weight loss, and any sore that does not heal.
