What is cancer?
The word cancer does not identify a single disease, but a group of diseases characterized by a pathological change in the cells of a specific tissue. Such change causes cells to multiply at an incontrollable rate, by-passing processes that, under normal conditions, would regulate their growth. In most types of cancer, cancerous cells tend to form agglomerations or masses called tumors. Cancerous cells do not respect
territorial limits which separate different tissues of the organism from one another, and are able to attack and invade contiguous tissues and organs. They can also detach themselves from the original mass and reach other parts of the body through blood and lymphatic circulation, thus originating new masses, called metastasis. The characteristics and the name given to the cancer are always associated to the area of its origin, even in the presence of a metastasis in another organ: a lung cancer that metastasizes in the bone, is still and will always be considered to be lung cancer, and not bone cancer, and consequently must be treated as such. The word cancer is equivalent to the word malignant tumor. However not all tumors are cancerous. Many of them are benign; a benign tumor does not grow or spread the same way a malignant tumor does, and generally it is not life threatening. A very small number of cancers, such as those that affect blood cells, do not form solid masses or tumors, but are called diffused diseases.