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DictionarySeecarcinoidEncyclopediaSeecarcinoid syndromecarcinoid tumor
tumor [too´mor] 1. swelling or morbid enlargement; this is one of the cardinal signs of inflammation.2. a new growth of tissue in which cell multiplication is uncontrolled and progressive. Tumors are also called neoplasms, which means that they are composed of new and actively growing tissue. Their growth is faster than that of normal tissue, continuing after cessation of the stimuli that evoked the growth, and serving no useful physiologic purpose. adj., adj tu´morous.
Tumors are classified in a number of ways, one of the simplest being according to their origin and whether they are malignant or benign. Tumors of mesenchymal origin include fibroelastic tumors and those of bone, fat, blood vessels, and lymphoid tissue; they may be benign or malignant (sarcoma). Tumors of epithelial origin are found in glandular tissue and such organs as the breast, stomach, uterus, or skin; they also may be either benign or malignant (carcinoma). Mixed tumors contain different types of cells derived from the same primary germ layer, and teratomas" >teratomas contain cells derived from more than one germ layer; both kinds may be benign or malignant.Benign Tumors. Benign tumors do not endanger life unless they interfere with normal functions of other organs or affect a vital organ. They grow slowly, pushing aside normal tissue but not invading it. They are usually encapsulated, well demarcated growths. They are not metastatic; that is, they do not form secondary tumors in other organs. Benign tumors usually respond favorably to surgical treatment and some forms of radiation therapy.Malignant Tumors. These tumors are composed of embryonic, primitive, or poorly differentiated cells. They grow in a disorganized manner and so rapidly that nutrition of the cells becomes a problem. For this reason necrosis and ulceration are characteristic of malignant tumors. They also invade surrounding tissues and are metastatic, initiating the growth of similar tumors in distant organs. (See also cancer.) Gross appearance of benign (A) and malignant (B) tumors. From Damjanov, 2000.benign tumor one that lacks the properties of invasiveness and metastasis and that is usually surrounded by a fibrous capsule; its cells also show a lesser degree of anaplasia than those of a tumor" >malignant tumor do. bladder tumor a tumor of the urinary bladder; see also bladder cancer.brain tumor see brain tumor" >brain tumor.brown tumor a giant-cell granuloma produced in and replacing bone, occurring in osteitis fibrosa cystica and due to hyperparathyroidism.Burkitt's tumor Burkitt's lymphoma.Buschke-Löwenstein tumor a slow-growing mass of warts found usually in the prepuce but sometimes elsewhere in the perianal region; it starts as a plaque and may grow into a large cauliflowerlike mass. Called also giant condyloma.carcinoid tumor carcinoid (def. 1).carotid body tumor a chemodectoma of a carotid body, found as a firm round mass at the bifurcation of the common carotid artery.connective tissue tumor any tumor arising from a connective tissue structure, such as a fibroma or sarcoma.desmoid tumor desmoid" >desmoid (def. 1).endodermal sinus tumor yolk sac tumor.erectile tumor cavernous hemangioma.Ewing's tumor Ewing's sarcoma.false tumor pseudotumor.fibroid tumor 1. fibroma.2. leiomyoma uteri.germ cell tumor any of a group of tumors arising from primitive germ cells, usually of the testis or ovum; they range from benign to highly malignant. Types include germinoma, tumor" >yolk sac tumor, teratoma, carcinoma" >embryonal carcinoma, and some types of choriocarcinoma; many tumors are mixtures of types.giant cell tumor 1. a benign or malignant tumor containing giant cells; see under carcinoma, granuloma, and sarcoma.2. a bone tumor, ranging from benign to frankly malignant, composed of cellular spindle cell stroma containing multinucleated giant cells resembling osteoclasts.3. a small yellow benign tumorlike nodule of tendon sheath origin, usually of the wrist and fingers or ankle and toes, laden with lipophages and containing multinucleated giant cells.glomus tumor 1. a blue-red, extremely painful chemodectoma involving an arteriovenous anastomosis or cluster of blood cells, which may be found anywhere in the skin, most often in the distal portion of the fingers and toes, especially beneath the nail. Such tumors may also occur in the stomach and nasal cavity.2. chemodectoma.granular cell tumor a relatively common neoplasm whose cells have a granular appearance by light microscopy; it is usually benign but occasionally malignant, and multiple tumors may occur. It can be found anywhere but is most often seen in the oral cavity, especially in the tongue.granulosa tumor (granulosa cell tumor) see granulosa cell tumor.granulosa-theca cell tumor see granulosa-theca cell tumor.heterologous tumor one made up of tissue differing from that in which it grows.homoiotypic tumor (homologous tumor) one made up of tissue resembling that in which it grows.Hürthle cell tumor see hürthle cell tumor.islet cell tumor a tumor of the islands of Langerhans; many secrete excessive amounts of hormones. Types include gastrinoma, glucagonoma, insulinoma, somatostatinoma, and vipoma.Krukenberg's tumor see krukenberg's tumor.lipoid cell tumor of ovary a usually benign ovarian tumor composed of eosinophilic cells or cells with lipoid vacuoles; it causes masculinization" >masculinization.tumor lysis syndrome severe hyperphosphatemia, hyperkalemia, hyperuricemia, and hypocalcemia occurring after effective induction chemotherapy of rapidly growing malignant neoplasms; thought to be due to release of intracellular products after cell lysis.malignant tumor one that has the properties of invasiveness and metastasis and that shows a greater degree of anaplasia than a tumor" >benign tumor does.mast cell tumor mastocytoma.melanotic neuroectodermal tumor a benign, rapidly growing, dark tumor of the jaw or occasionally some other site, almost always seen in infants; called also melanoameloblastoma.mixed tumor one composed of more than one type of neoplastic tissue.tumor necrosis factor receptor–associated periodic syndrome (TRAPS) familial periodic fever.organoid tumor teratoma.peripheral neuroectodermal tumor (PNET) any of a heterogeneous group of neoplasms originating in supporting structures or neuronal tissue, primarily of the extremities, pelvis, or chest wall; seen most often in adolescents and young adults and frequently having widespread metastases.plasma cell tumor 1. plasma cell dyscrasias.2. solitary myeloma.sand tumor psammoma.Sertoli-Leydig cell tumor androblastoma (def. 1).theca cell tumor a fibroidlike tumor of the ovary containing yellow areas of fatty material derived from theca cells.turban t's multiple cylindromas of the scalp that are grouped together so as to cover the entire scalp.Wilms' tumor a rapidly developing malignant mixed tumor of the kidneys, made up of embryonal elements, occurring chiefly in children before the seventh year; a genetic component is suspected in its etiology. It may be accompanied by congenital defects such as urinary tract abnormalities, absent iris of the eye, and asymmetry of parts. With treatment, the prognosis is excellent. Called also embryonal carcinosarcoma and nephroblastoma.yolk sac tumor a malignant tumor" >germ cell tumor of children that represents a proliferation of both yolk sac endoderm and extraembryonic mesenchyme. It produces α-fetoprotein and most often occurs in the testes, but is also seen in the ovaries and some extragonadal sites. Called also endodermal sinus tumor.car·ci·noid tu·mora usually small, slow-growing neoplasm composed of islands of rounded, oxyphilic, or spindle-shaped cells of medium size, with moderately small vesicular nuclei, and covered by intact mucosa with a yellow cut surface; neoplastic cells are frequently palisaded at the periphery of the small groups, and the latter have a tendency to infiltrate surrounding tissue. Such neoplasms occur anywhere in the gastrointestinal tract (and in the lungs and other sites), with approximately 90% in the appendix and the remainder chiefly in the ileum, but also in the stomach, other parts of the small intestine, the colon, and the rectum; those of the appendix and small tumors seldom metastasize, but reported incidences of metastases from other primary sites and from tumors exceeding 2.0 cm in diameter vary from 25-75%; lymph nodes in the abdomen and the liver may be conspicuously involved, but metastases above the diaphragm are rare. About 1% of cases are associated with the carcinoid syndrome, usually after the portal circulation is bypassed as in cases involving liver metastases.
See also: carcinoid syndrome. car·ci·noid tu·mor (kahr'si-noyd tū'mŏr) A neoplasm composed of cells of medium size, with moderately small vesicular nuclei; neoplastic cells are frequently palisaded at the periphery of small groups. Such neoplasms occur in the gastrointestinal tract, the lungs, and other sites, with approximately 90% in the appendix.
See also: carcinoid syndrome
Synonym(s): argentaffinoma. ThesaurusSeetumor |