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Related to neoplasm: malignant neoplasm, Benign neoplasm, Lung neoplasm




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., cancerscancer,
in medicine, common term for neoplasms, or tumors, that are malignant. Like benign tumors, malignant tumors do not respond to body mechanisms that limit cell growth.
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, 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 leukemiasleukemia
, cancerous disorder of the blood-forming tissues (bone marrow, lymphatics, liver, spleen) characterized by excessive production of immature or mature leukocytes (white blood cells; see blood) and consequently a crowding-out of red blood cells and platelets.
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 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.


An aberrant new growth of abnormal cells or tissues; a tumor.
References in periodicals archive ?
This report describes the clinical and pathologic findings of an unusual bilateral renal tubular neoplasm in an adult male channel-billed toucan.
These are highly aggressive neoplasms metastasizing commonly to lung, liver, and bone.
The number of reported cases of this rare neoplasm has increased since the report of Ave cases by Kloppel (2) in 1981.
Mixed epithelial and stromal tumor (MEST) is a rare neoplasm, composed of both epithelial and stromal elements and demonstrating solid and cystic architecture.
Primary neoplasms of the appendix: radiologic spectrum of disease with pathologic correlation.
2%) were confirmed malignant and 1 was classified as a Hurthle cell neoplasm of uncertain malignant potential.
The differential diagnosis includes simple cysts, echinococcal cysts, liver abscesses, cystic degeneration of a liver neoplasm, Caroli's disease, posttraumatic cysts, and polycystic diseases.
Rondagh and colleagues hypothesized that this difference might be balanced by a greater prevalence of nonpolypoid colorectal neoplasms (NP-CRNs) in women.
Radiotherapy and chemotherapy are also associated with an increased risk of developing a second malignant neoplasm in childhood.
com/research/2gxvfh/malignant_neoplasm) has announced the addition of Global Markets Direct's new report "Malignant Neoplasms - Pipeline Review, H2 2012" to their offering.
Histopathologic examination of the neoplasm revealed that it was a malignant melanoma.
Atypical cells, rule out Hurthle cell neoplasm, had 2 different patterns that have been described previously.