Malignant Tumors

For the naming of malignant tumours, the rules for using prefixes and suffixes are similar to those used to designate benign neoplasms. The suffix -sarcoma indicates neoplasms that arise in mesenchymal tissues — for instance, in supportive or connective tissue such as muscle or bone. The suffix -carcinoma, on the other hand, indicates an epithelial origin.

As with benign tumours, a prefix indicates the predominant cell type in the tumour. Thus, a liposarcoma arises from a precursor to a fat cell called a lipoblastic cell; a myosarcoma is derived from precursor muscle cells (myogenic cells); and squamous-cell carcinoma arises from the outer layers of mucous membranes or the skin (composed primarily of squamous, or scalelike, cells).

Just as adenoma designates a benign tumour of epithelial origin that takes on a glandlike structure, so adenocarcinoma designates a malignant epithelial tumour with a similar growth pattern. Usually the term is followed by the organ of origin — e.g., adenocarcinoma of the lung.

Malignant tumours of the blood-forming tissue are designated by the suffix -emia (Greek: ''blood''). Thus, leukemia refers to a cancerous proliferation of white blood cells (leukocytes). Cancerous tumours that arise in lymphoid organs, such as the spleen, thymus, or lymph glands, are termed malignant lymphomas. The term lymphoma is often used without the qualifier malignant to denote cancerous lymphoid tumours; however, this usage is confusing, since the suffix -oma, as mentioned above, more properly designates a benign neoplasm.

The suffix -oma is also used to designate other malignancies, such as seminoma, which is a malignant tumour that arises from the germ cells of the testis. In a similar manner, malignant tumours of melanocytes (the skin cells that produce the pigment melanin) should be called melanocarcinomas, but for historical reasons the term melanoma persists.

In some instances neoplasms are named for the physician who first described them. For example, the malignant lymphoma called Hodgkin disease was described in 1832 by the English physician Thomas Hodgkin. Burkitt lymphoma is named after the British surgeon Denis Parsons Burkitt; Ewing sarcoma of bone was described by James Ewing; and nephroblastoma, a malignant tumour of the kidney in children, is commonly called Wilms tumour, for the German surgeon Max Wilms.

The site of origin of a tumour, which is so important in its classification and naming (as explained above), also is an important determinant of the way a tumour will grow, how fast it will give rise to clinical symptoms, and how early it may be diagnosed. For example, a tumour of the skin located on the face is usually detected very early, whereas a sarcoma located in the deep soft tissues of the abdomen can grow to weigh 2 kilograms (5 pounds) before it causes much of a disturbance. The site of origin of a tumour also determines the signs and symptoms of disease that the individual will experience and influences possible therapeutic options.