Pathology

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neoplasm

The Columbia Encyclopedia, 6th ed. | 2008 | Copyright

neoplasm or tumor, tissue composed of cells that grow in an abnormal way. Normal tissue is growth-limited, i.e., cell reproduction is equal to cell death. Feedback controls limit cell division after a certain number of cells have developed, allowing for tissue repair but not expansion. Tumor cells are less responsive to these restraints and can proliferate to the point where they disrupt tissue architecture, distort the flow of nutrients, and otherwise do damage.

Tumors may be benign or malignant. Benign tumors remain localized as a discrete mass. They may differ appreciably from normal tissue in structure and excessive growth of cells, but are rarely fatal. However, even benign tumors may grow large enough to interfere with normal function. Some benign uterine tumors, which can weigh as much as 50 lb (22.7 kg), displace adjacent organs, causing digestive and reproductive disorders. Benign tumors are usually treated by complete surgical removal. Cells of malignant tumors, i.e., cancers , have characteristics that differ from normal cells in other ways beside cell proliferation. For example, they may be deficient in some specialized functions of the tissues where they originate. Malignant cells are invasive, i.e., they infiltrate surrounding normal tissue; later, malignant cells metastasize, i.e., spread via blood and the lymph system to other sites.

Both benign and malignant tumors are classified according to the type of tissue in which they are found. For example, fibromas are neoplasms of fibrous connective tissue, and melanomas are abnormal growths of pigment (melanin) cells. Malignant tumors originating from epithelial tissue, e.g., in skin, bronchi, and stomach, are termed carcinomas. Malignancies of epithelial glandular tissue such as are found in the breast, prostate, and colon, are known as adenocarcinomas. Malignant growths of connective tissue, e.g., muscle, cartilage, lymph tissue, and bone, are called sarcomas. Lymphomas and leukemias are malignancies arising among the white blood cells. A system has been devised to classify malignant tissue according to the degree of malignancy, from grade 1, barely malignant, to grade 4, highly malignant. In practice it is not always possible to determine the degree of malignancy, and it may be difficult even to determine whether particular tumor tissue is benign or malignant.

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neoplasm

The Oxford Companion to the Body | 2001 | | Copyright

neoplasm From the Greek ‘new’ and ‘form’: an abnormal growth of tissue, or tumour. A neoplasm can be benign or malignant. The name given to any particular tumour is an indication of the type of tissue from which it arises, plus the ending ‘-oma’. Benign growths range from small warts to huge ovarian cysts; they include fatty lumps (lipomas), bony excrescences (osteomas), and many others. Malignant growths (cancers) are broadly classified according to the type of cells they arise from as either carcinoma, from epithelial sites — body coverings or linings (e.g. skin, breast, colon) — or sarcoma, from deeper tissue (e.g. bone or muscle). Malignant neoplasms are characterized by being locally invasive and by forming metastases — seeding in other parts of the body via lymphatic or blood vessels. A malignant growth may therefore be primary — at the original site — or secondary, metastatic.

Stuart Judge

neoplasm

The Oxford Pocket Dictionary of Current English | 2009 | Copyright

ne·o·plasm / ˈnēəˌplazəm/ • n. a new and abnormal growth of tissue in some part of the body, esp. as a characteristic of cancer.

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neoplasm

A Dictionary of Biology | 2004 | Copyright

neoplasm (tumour) Any new abnormal growth of cells, forming either a harmless (benign) tumour or a malignant one (see cancer).

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neoplasm

A Dictionary of Nursing | 2008 | Copyright

neoplasm (nee-oh-plazm) n. any new and abnormal growth: a benign or malignant tumour.
—neoplastic adj.

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