osteoclastoma

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 contain cells derived from more than one germ layer; both kinds may be benign or malignant.

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 malignant tumor do.

bladder tumor a tumor of the urinary bladder; see also bladder cancer.

brain tumor see 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 (def. 1).

endodermal sinus tumor yolk sac tumor.

erectile tumor cavernous hemangioma.

Ewing's tumor Ewing's sarcoma.

false tumor pseudotumor.

fibroid tumor

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, yolk sac tumor, teratoma, embryonal carcinoma, and some types of choriocarcinoma; many tumors are mixtures of types.

giant cell tumor

glomus tumor

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.

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 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

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 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.