- 1. Any swelling or tumefaction. 2. SYN: neoplasm. 3. One of the four signs of inflammation (t., calor, dolor, rubor) enunciated by Celsus. [L. t., a swelling]- acinar cell t. a solid and cystic t. of the pancreas, occurring in young women; t. cells contain zymogen granules.- acute splenic t. acute splenitis, enlargement, and softening of the spleen, usually due to bacteremia or severe bacterial toxemia.- adenomatoid t. a small benign t. of the male epididymis and female genital tract, consisting of fibrous tissue or smooth muscle enclosing anastomosing glandlike spaces containing acid mucopolysaccharide lined by flattened cells that have ultra-structural characteristics of mesothelial cells. SYN: benign mesothelioma of genital tract.- adenomatoid odontogenic t. a benign epithelial odontogenic t. appearing radiographically as a well-circumscribed, radiolucent-radiopaque lesion usually surrounding the crown of an impacted tooth in an adolescent or young adult; characterized histologically by columnar cells organized in a ductlike configuration interspersed with spindle-shaped cells and amyloidlike deposition that gradually undergoes dystrophic calcification. SYN: adenoameloblastoma, ameloblastic adenomatoid t..- amyloid t. SYN: nodular amyloidosis.- benign t. a t. that does not form metastases and does not invade and destroy adjacent normal tissue. SYN: innocent t..- borderline ovarian t. an ovarian surface epithelial t. in which the growth pattern is intermediate between benign and malignant; includes mucinous, serous, endometrioid, and Brenner tumors of the ovary; highly curable but may recur after surgical removal. SYN: low malignant potential t..- Brenner t. a relatively infrequent benign neoplasm of the ovary, consisting chiefly of fibrous tissue that contains nests of cells resembling transitional type epithelium, as well as glandlike structures that contain mucin; origin is controversial, but it may arise from the Walthard cell rest; ordinarily found incidentally in ovaries removed for other reasons, especially in postmenopausal women.- brown t. a mass of fibrous tissue containing hemosiderin-pigmented macrophages and multinucleated giant cells, replacing and expanding part of a bone in primary hyperparathyroidism.- calcifying epithelial odontogenic t. a benign epithelial odontogenic neoplasm derived from the stratum intermedium of the enamel organ; a painless, slowly growing, mixed radiolucent-radiopaque lesion characterized histologically by cords of polyhedral epithelial cells, deposits of amyloid, and spherical calcifications. SYN: Pindborg t..- carcinoid t. a 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 metatases from other primary sites and from tumors exceeding 2.0 cm in diameter vary from 25–75%; lymph node s in the abdomen and the liver may be conspicuously involved, but metastases above the diaphragm are rare. SEE ALSO: carcinoid syndrome.- cellular t. a t. composed mainly of closely packed cells.- collision t. two originally separate tumors, especially a carcinoma and a sarcoma, that appear to have developed by chance in close proximity, so that an area of mingling exists. SEE ALSO: carcinosarcoma.- dermal duct t. a benign small t. derived from the intradermal part of eccrine sweat gland ducts occurring often on the head and neck.- desmoplastic small cell t. a high-grade malignant t. found most often in the abdomen of adolescent males; typically t. cells contain both desmin and keratin, i.e., show hybrid features like fetal mesothelial cells; the exact nature of these cells remains unknown.- dysembryoplastic neuroepithelial t. a rare low-grade neoplasm most frequently seen in children and associated with seizures and cortical dysplasia; the often multinodular, multicystic t. is composed of oligodendroglial-like cells with accompanying neurons.- embryonal t., embryonic t. a neoplasm, usually malignant, which arises during intrauterine or early postnatal development from an organ rudiment or immature tissue; it forms immature structures characteristic of the part from which it arises, and may form other tissues as well. The term includes neuroblastoma and Wilms t., and is also used to include certain neoplasms presenting in later life, this usage being based on the belief that such tumors arise from embryonic rests. SEE ALSO: teratoma. SYN: embryoma.- endocervical sinus t. malignant germ cell t. commonly found in the ovary. The t. arises from primitive germ cells and develops into extra-embryonic tissue resembling the yolk sac. SYN: yolk sac carcinoma.- endodermal sinus t. a malignant neoplasm occurring in the gonads, in sacrococcygeal teratomas, and in the mediastinum; produces α-fetoprotein and is thought to be derived from primitive endodermal cells. SYN: yolk sac t..- endometrioid t. a t. of the ovary containing epithelial or stromal elements resembling tumors of the endometrium.- Ewing t. a malignant neoplasm which occurs usually before the age of 20 years, about twice as frequently in males, and in about 75% of patients involves bones of the extremities, including the shoulder girdle, with a predilection for the metaphysis; histologically, there are conspicuous foci of necrosis in association with irregular masses of small, regular, rounded, or ovoid cells (2–3 times the diameter of erythrocytes), with very scanty cytoplasm. SYN: endothelial myeloma, Ewing sarcoma.- gastrointestinal autonomic nerve t. benign or malignant t. of stomach and small intestine histogenetically related to myenteric plexus; may be familial and related to gastrointestinal neuronal dysplasia.- gastrointestinal stromal t. benign or malignant t. composed of unclassifiable spindle cells; immunohistochemically distinct from smooth muscle and Schwann cell tumors.- giant cell t. of bone a soft, reddish-brown, sometimes malignant, osteolytic t. composed of multinucleated giant cells and ovoid or spindle-shaped cells, occurring most frequently in an end of a long tubular bone of young adults. SYN: giant cell myeloma, osteoclastoma.- giant cell t. of tendon sheath a nodule, possibly inflammatory in nature, arising commonly from the flexor sheath of the fingers and thumb; composed of fibrous tissue, lipid- and hemosiderin-containing macrophages, and multinucleated giant cells. SYN: localized nodular tenosynovitis.- glomus t. [MIM*138000] a vascular neoplasm composed of specialized pericytes (sometimes termed glomus cells), usually in single encapsulated nodular masses that may be several millimeters in diameter and occur almost exclusively in the skin, often subungually in the upper extremity; it is exquisitely tender and may be so painful that patients voluntarily immobilize an extremity, sometimes leading to atrophy of muscles; multiple glomus tumors occur, sometimes with autosomal dominant inheritance. Tumors with cavernous spaces lined by glomus cells are called glomangiomas.- glomus jugulare t. a glomus t. arising from the jugular glomus and usually presenting initially in the hypotympanum.- granular cell t. a microscopically specific, generally benign t., often involving peripheral nerves in skin, mucosa, or connective tissue, derived from Schwann cells; the abundant cytoplasm contains lysosomal granules, the cells infiltrate between adjacent tissues although growth is slow, and adjacent surface epithelium may show hyperplasia.- granulosa cell t. a benign or malignant t. of the ovary arising from the membrana granulosa of the vesicular ovarian (graafian) follicle and frequently secreting estrogen; it is soft, solid, white or yellow, and consists of small round cells sometimes enclosing Call-Exner bodies; larger lipid-containing cells may be present. SYN: folliculoma (1).- islet cell t. an endocrine t. composed of cells equivalent or related to those in the normal islet of Langerhans; may be benign or malignant; usually hormonally active; comprises insulinomas, glucagonomas, vipomas, somatostatinomas, gastrinomas, pancreatic polypeptide-secreting t., and multihormonal or hormonally inactive pancreatic islet cell tumors.- juxtaglomerular cell t. a t. of juxtaglomerular cell origin usually presenting with symptoms of secondary aldosteronism, including severe diastolic hypertension, which appears to be due to t.-produced renin. The histologic appearance resembles that of a hemangiopericytoma.- Krukenberg t. a metastatic carcinoma of the ovary, usually bilateral and secondary to a mucous carcinoma of the stomach, which contains signet-ring cells filled with mucus.- Landschutz t. a transplantable, possibly isoantigenic, highly virulent neoplasm which can be grown in any strain of mice; the host is killed in a few days by what is apparently an anaplastic carcinoma.- Leydig cell t. a testicular and, less commonly, ovarian neoplasm composed of Leydig cells, usually benign but may be malignant; may secrete androgens or estrogens. SYN: interstitial cell t. of testis.- malignant t. a t. that invades surrounding tissues, is usually capable of producing metastases, may recur after attempted removal, and is likely to cause death of the host unless adequately treated. SEE ALSO: cancer.- melanotic neuroectodermal t. of infancy a benign neoplasm of neuroectodermal origin that most often involves the anterior maxilla of infants in the first year of life. It presents clinically as a rapidly growing blue-black lesion producing a destructive radiolucency; histologically, it is characterized by small, round, undifferentiated t. cells interspersed with larger polyhedral melanin-producing cells arranged in an alveolar configuration. SYN: melanoameloblastoma, pigmented ameloblastoma, pigmented epulis, progonoma of jaw, retinal anlage t..- Merkel cell t. a rare malignant cutaneous t. seen in sun-exposed skin of elderly patients composed of dermal nodules of small round cells with scanty cytoplasm in a trabecular pattern; the t. cells contain cytoplasmic dense core granules resembling neurosecretory granules seen in Merkel cells. SYN: primary neuroendocrine carcinoma of the skin, trabecular carcinoma.- mesonephroid t. SYN: mesonephroma.- mixed t. a t. composed of two or more varieties of tissue.- mixed mesodermal t. a sarcoma of the body of the uterus arising in older women, composed of more than one mesenchymal tissue, especially including striated muscle cells. SYN: malignant mixed müllerian t..- mixed t. of salivary gland a t. composed of salivary gland epithelium and fibrous tissue with mucoid or cartilaginous areas. SYN: pleomorphic adenoma.- oil t. SYN: lipogranuloma.- organoid t. a t. of complex structure, glandular in origin, containing epithelium, connective tissue, etc.- Pancoast t. any carcinoma of the lung apex causing the Pancoast syndrome by invasion or compression of the brachial plexus and stellate ganglion. SYN: superior pulmonary sulcus t..- papillary t. SYN: papilloma.- phantom t. accumulation of fluid in the interlobar spaces of the lung, secondary to congestive heart failure, radiologically simulating a neoplasm.- phyllodes t. a spectrum of neoplasms consisting of a mixture of benign epithelium and stroma with variable cellularity and cytologic abnormalities, ranging from benign phyllodes t. to cytosarcoma phyllodes; most often involves the breast.- pilar t. of scalp a solitary t. of the scalp in elderly women that may ulcerate; microscopically resembles squamous cell carcinoma composed of glycogen-rich clear cells, but is benign. SYN: proliferating tricholemmal cyst.- Pinkus t. SYN: fibroepithelioma.- placental site trophoblastic t. a t. usually arising in the uterus of parous women during reproductive years. Histologically, the t. consists of a predominance of intermediate trophoblastic cells with fibrinoid material and vascular invasion.- pontine angle t. a t. in the angle formed by the cerebellum and the lateral pons, often refers to an acoustic schwannoma.- pregnancy t. SYN: granuloma gravidarum.- primitive neuroectodermal t. a designation used to refer to a group of morphologically similar embryonal neoplasms that arise in intracranial and peripheral sites of the nervous system and which may show various degrees of cellular differentiation; includes medulloblastoma, pineoblastoma, etc.- Sertoli cell t. a t. of testis or ovary composed of Sertoli cells; most often benign but may be malignant.- Sertoli-Leydig cell t. an ovarian t. composed of Sertoli and Leydig cells; may secrete androgens. SYN: arrhenoblastoma, gynandroblastoma (1).- Sertoli-stromal cell t. a generic term for ovarian sex-cord stromal t. composed of Sertoli cells, Leydig cells, and cells resembling rete epithelial cells, either in a pure form or as a mixture of these cell types.- solitary fibrous t. a benign t. of fibrous tissue which usually arises in the pleural space on other sites. SYN: benign mesothelioma.- squamous odontogenic t. a benign epithelial odontogenic t. thought to arise from the epithelial cell rests of Malassez; appears clinically as a radiolucent lesion closely associated with the tooth root and histologically as islands of squamous epithelium enclosed by a peripheral layer of flattened cells.- steroid cell t. a collective term used for ovarian tumors composed of cells resembling steroid-secreting lutein cells; comprises several tumors such as stromal luteoma, Leydig cell t., steroid cell t. not otherwise specified; hormonally active; may be benign or malignant. SYN: hilar cell t. of ovary.- triton t. a peripheral nerve t. with striated muscle differentiation, seen most often in neurofibromatosis; named after the Masson theory of transformation of motor nerve fibers into muscle in triton salamanders.- Wilms t. a malignant renal t. of young children, composed of small spindle cells and various other types of tissue, including tubules and, in some cases, structures resembling fetal glomeruli, and striated muscle and cartilage. Often inherited as an autosomal dominant trait [MIM*194070, *194080, *194090]. SYN: nephroblastoma.- Zollinger-Ellison t. a non–beta cell t. of pancreatic islets causing the Zollinger-Ellison syndrome.
* * *tu·mor or chiefly Brit tu·mour 't(y)ü-mər n an abnormal benign or malignant new growth of tissue that possesses no physiological function and arises from uncontrolled usu. rapid cellular proliferation see CANCER (1), CARCINOMA, SARCOMAtu·mor·like -.līk adj
* * *n.swelling: one of the classical signs of inflammation in a tissue, the other three being calor (heat), rubor (redness), and dolor (pain). The swelling of an inflamed area is due to the leakage from small blood vessels of clear protein-containing fluid, which accumulates between the cells.
* * *tu·mor (tooґmər) [L., from tumere to swell] 1. swelling, one of the cardinal signs of inflammation; morbid enlargement. 2. a new growth of tissue in which the multiplication of cells is uncontrolled and progressive; called also neoplasm.
See also under specific types of tumors, e.g., angioma, sarcoma.
Medical dictionary. 2011.