teratoma

A neoplasm composed of multiple tissues, including tissues not normally found in the organ in which it arises. Teratomas occur most frequently in the ovary, where they are usually benign and form dermoid cysts; in the testis, where they are usually malignant; and, uncommonly, in other sites, especially the midline of the body. SYN: teratoid tumor. [terato- + G. -oma, tumor]

- t. orbitae SYN: orbitopagus.

- sacrococcygeal t. found in the region of the tailbud. Most common tumor in the newborn period.

- triphyllomatous t. a t. composed of tissues derived from all three germ layers. SYN: tridermoma.

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ter·a·to·ma .ter-ə-'tō-mə n, pl -mas also -ma·ta -mət-ə a tumor derived from more than one embryonic layer and made up of a heterogeneous mixture of tissues (as epithelium, bone, cartilage, or muscle)

ter·a·to·ma·tous -mət-əs adj

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n.

a tumour composed of a number of tissues not usually found at that site. Teratomas most frequently occur in the testis and ovary, possibly derived from remnants of embryological cells that have the ability to differentiate into many types of tissue. Malignant teratoma of the testis is found in young men: it is more common in patients with a history of undescended testis. Like seminoma, it frequently occurs as a painless swelling of one testis (pain is not a good indication that the swelling is benign). Treatment is by orchidectomy avoiding an incision into the scrotum. The tumour can spread to lymph nodes, lungs, and bone, treatment of which may involve the use of chemotherapy drugs, such as vinblastine, bleomycin, cisplatin, and etoposide, with a high cure rate even in metastatic disease. Teratomas often produce alpha-fetoprotein, beta human chorionic gonadotrophin, or both; the presence of these substances (tumour marker) in the blood is a useful indication of the amount of tumour and the effect of treatment.

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ter·a·to·ma (ter″ə-toґmə) pl. teratomas, teratoґmata [terat- + -oma] a type of germ cell tumor derived from pluripotent cells and made up of elements of different types of tissue from one or more of the three germ cell layers; most often found in the ovary or testis in adults and in the sacrococcygeal region in children. Teratomas range from benign (mature, dermoid, and cystic) to malignant (immature and solid). Called also dysembryoma, teratoblastoma, organoid tumor, and teratoid tumor. teratomatous adj

Opened mature cystic teratoma (dermoid cyst) of the ovary, containing a mixture of tissues, including hair (bottom).