This gradual increase in the number of dividing cells creates a growing mass of tissue called a "tumor" or "neoplasm." If the rate of cell division is relatively rapid, and no "suicide" signals are in place to trigger cell death, the tumor will grow quickly in size; if the cells divide more slowly, tumor growth will be slower. But regardless of the growth rate, tumors ultimately increase in size because new cells are being produced in greater numbers than needed. As more and more of these dividing cells accumulate, the normal organization of the tissue gradually becomes disrupted. N.B:A neoplasm can be benign, potentially malignant (pre-cancer), or malignant (cancer). Neoplastic tumors often contain more than one type of cell, but their initiation and continued growth is usually dependent on a single population of neoplastic cells. These cells are presumed to be clonal - that is, they are descended from a single progenitor cell. Neoplasia vs. tumor Tumor (Latin for swelling, one of the cardinal signs of inflammation) originally meant any form of swelling, neoplastic or not. Current English, however, both medical and non-medical, uses tumor as a synonym of neoplasm. Some neoplasms do not form a tumor. These include leukemia and most forms of carcinoma in situ. source 1:Neoplasm - Wikipedia, the free encyclopedia source 2:Comprehensive Cancer Information - National Cancer Institute
