cancer - Classification - Nomenclature
The following closely related terms may be used to designate abnormal growths:

• Neoplasm: a scientific term which refers to an abnormal proliferation of genetically altered cells.
• Malignant neoplasm: synonymous with cancer.
• Tumor: broadly defined, can be any swelling or mass. However, the vast majority of entities referred to as 'tumors' in common usage are in fact neoplasms. Specifically, a tumor is a solid neoplasm ; some neoplasms, such as cancers of the blood, are not solid.
• Benign tumor: a tumor (solid neoplasm) that has self-limiting growth and does not invade other tissues nor metastasize. Usually not cancerous.
• Pre-malignancy: A non-invasive neoplasm that may not form an obvious mass, but has the potential to progress to cancer if left untreated. Pre-malignant neoplasms may show distinctive microscopic changes such as dysplasia or atypia.

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.
• Sarcoma: Malignant tumors derived from connective tissue, or mesenchymal cells.
• Lymphoma and leukemia: Malignancies derived from hematopoetic (blood-forming) cells
• Germ cell tumor: Tumors derived from totipotent cells. In adults most often found in the testicle and ovary; in fetuses, babies, and young children most often found on the body midline, particularly at the tip of the tailbone; in horses most often found at the poll (base of the skull).
• Blastic tumor: A tumor (usually malignant) which resembles an immature or embryonic tissue. Many of these tumors are most common in children.

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.

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