Medically, cancer is known as malignant neoplasm. However, a growth or a tumor may be benign or malignant. The three properties that differentiate self-limiting benign tumors from malignant cancer are:

-    Uncontrolled growth, which is division and multiplication beyond normal limits
-    Invasion, which is intrusion and destruction of adjacent cells
-    And sometimes metastasis, which is spread to other locations in the body through lymph nodes or blood.

Cancer is basically a disease of regulation of growth of tissue and with the exception of leukemia, most cancers form tumors. For the disease to spread and develop further in the body, a normal cell must change into a cancer cell. The common course in all cancers is the alteration in the genetic material of a cancerous cell and its progeny.

According to a report published in January 2006 in the National Geographic “there is compelling evidence that cancers hidden beneath the skin can be detected simply by (dogs) examining a person’s breath.” While the basis of this news may be debatable till is conclusively proven, cancer remains a medical condition that is usually detected very late in humans as well as dogs.