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

• Neoplasia and neoplasm are the scientific designations for cancerous diseases. This group contains a large number of different diseases. Neoplasms can be benign or malignant.

• Cancer is a widely used word that is usually understood as synonymous with malignant neoplasm. It is occasionally used instead of carcinoma, a sub-group of malignant neoplasms. Because of its overwhelming popularity relative to 'neoplasia', it is used frequently instead of 'neoplasia', even by scientists and physicians, especially when discussing neoplastic diseases as a group.

• Tumor in medical language simply means swelling or lump, either neoplastic, inflammatory or other. In common language, however, it is synonymous with 'neoplasm', either benign or malignant. This is inaccurate since some neoplasms usually do not form tumors, for example leukemia or carcinoma in situ.

Cancers are classified by the type of cell that resembles the tumor and, therefore, the tissue presumed to be the origin of the tumor. The following general categories are usually accepted:

• Carcinoma: malignant tumors derived from epithelial cells. This group represent 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 tumours: tumors derived from germ cells, normally found in the testicle and ovary

• Choriocarcinoma: malignant tumors derived from the placenta

Malignant tumors are usually named using the Latin or Greek root of the organ as a prefix and the above category name as the suffix. For instance, a malignant tumor of liver cells 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. For instance, a benign tumor of the smooth muscle of the uterus is called leiomyoma (the common name of this frequent tumor is fibroid). This nomenclature is however somewhat inconsistent, since several "malignant" tumor growths also have this suffix in their names, e.g. neuroblastoma, lymphoma and melanoma.