Nomenclature and classification

The following closely related terms may be used to designate abnormal growths:

* Neoplasia and neoplasm are scientific terms which refer to abnormal proliferations of genetically altered cells.

* Cancer is synonymous with malignant neoplasm.

* Benign tumors or benign neoplasms are similar to cancers in that they are composed of genetically abnormal cells which grow in excess of any normal process. However, the growth of benign tumors is self-limiting, and they do not invade other tissues or metastasize.

* Tumor originally referred to any swelling or mass, either neoplastic, inflammatory or other. However, the vast majority of entities referred to as tumors in common usage are in fact neoplasms (although many are benign, and thus not cancers).

* A paraneoplastic phenomenon is a physiological disturbance associated with a neoplasm, but not related to the physical effects of a tumor mass or invasive tumor cells themselves. Disturbances can be hormonal, neurological, hematological, or biochemical.

Cancers are classified by the type of cell that resembles the tumor and, therefore, the tissue presumed to be the origin of the tumor. Examples of general categories include:

* Carcinoma: malignant tumors derived from epithelial cells. This group represents the most common cancers, including the common forms of breast, prostate, lung and colon cancer.

* Lymphoma and Leukemia: malignant tumors derived from blood and bone marrow cells

* Sarcoma: malignant tumors derived from connective tissue, or mesenchymal cells

* Mesothelioma: tumors derived from the mesothelial cells lining the peritoneum and the pleura.

* Glioma: tumors derived from glia, the most common type of brain cell

* Germ cell tumor: tumors derived from reproductive cells, most commonly found in the testicle and ovary

Malignant tumors are usually named using the Latin or Greek root of the organ of origin as a prefix and the above category name as the suffix. For instance, a malignant tumor of the liver is called hepatocarcinoma; a malignant tumor of the fat cells is called liposarcoma. For common cancers, the English organ name is used. For instance, the most common type of breast cancer is called ductal carcinoma of the breast or mammary ductal carcinoma. Here, the adjective ductal refers to the appearance of the cancer under the microscope, resembling normal breast ducts.

Benign tumors are named using -oma as a suffix with the organ name as the root. For instance, a benign tumor of the smooth muscle of the uterus is called leiomyoma (the common name of this frequent tumor is fibroid). However, some cancers also use this prefix for historical reasons, examples being melanoma and seminoma.