Cancer Type

Cancer is the common term for aggressive and usually fatal forms of a large class of diseases known as neoplasms. A neoplasm is described as being relatively autonomous because it does not fully obey the biological mechanisms that govern the growth and metabolism of individual cells and the overall cell interactions of the living organism. Some neoplasm grow more rapidly than the tissues from which they arise; others grow at a normal pace but because of other factors eventually become recognizable as abnormal growths. The changes seen in a neoplasm are heritable in that these characteristics are passed on from each cell to its progeny, or daughter cells.

Classification of neoplasm as either benign or malignant relates to their behavior. A benign neoplasm, for instance, is encapsulated; malignant neoplasms are not. Malignancies grow more rapidly than do benign forms and invade adjacent, normal tissue. Tissue of a benign tumor is structured similarly to the tissue from which it is derived; malignant tissue has an abnormal and unstructured appearance. Most malignant tumors, in fact, show abnormalities in chromosome structure, that is, the structure of the DNA molecules that constitute the genetic materials duplicated and passed on the later generations of cells. Most important, benign neoplasm do not metastasize, that is, begin to grow at sites other than the point of origin, whereas malignant tumors do. The term cancer always denotes a malignant neoplasm, whereas the term of Tumor indicates a readily defined mass of tissue distinguishable from normal living tissue.