malignant teratoma

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a type of germ cell tumor made up of a number of different types of tissue from one or more of the germ cell layers; it is usually found in the ovary or testis and may be either benign or malignant.
malignant teratoma a solid, malignant ovarian tumor resembling a dermoid cyst but composed of immature embryonal or extraembryonal elements derived from all three germ layers.
Miller-Keane Encyclopedia and Dictionary of Medicine, Nursing, and Allied Health, Seventh Edition. © 2003 by Saunders, an imprint of Elsevier, Inc. All rights reserved.

immature teratoma

A teratoma with both mature elements from all 3 germ-cell layers (ectodermal, mesodermal, and endodermal), and immature (embryonic, not foetal) tissues, most commonly of neural origin, consisting of primitive neurotubules, neuroepithelial rosettes, immature glial elements, immature ependyma, primitive muscle.

Relatively good if under age 15; guarded if adult (see table).

Grade, Immature teratoma
I)  ≤ 1 focus/slide contains immature tissue—low-grade.
II)  2–3 foci contains immature tissue—high-grade, adjuvant radiation therapy; survival possible.
III) 4+ foci contains immature tissue—high-grade, adjuvant radiation therapy; prognosis very poor.

Based on any immature tissue on any 1 slide at 40X (low-power field).

Immature teratomas behave differently in children; grading is unnecessary, the only histological predictor of recurrence is the presence of foci of yolk-sac tumour (confirmed by IHC stains for CK, AFP, glypican 3, SALL4); immature neural tissue does not indicate malignancy in immature teratomas of infants as it does in adults.
Segen's Medical Dictionary. © 2012 Farlex, Inc. All rights reserved.

malignant teratoma

Immature teratoma, see there.
McGraw-Hill Concise Dictionary of Modern Medicine. © 2002 by The McGraw-Hill Companies, Inc.
References in periodicals archive ?
Our case was the rarest case reported by us about the mature cystic teratoma with malignant differentiation to squamous cell carcinoma arising from mesocolon of sigmoid region with only one case reported in 2007 with malignant teratoma arising from mesentry of descending colon as per the MEDLINE Database (12).
They show a high predisposition to ovarian cancer with the most frequent observed histotypes are gonadoblastomas and dysgerminomas, followed by Brenner tumors, malignant teratomas, and mixed endodermal sinus tumors.[sup][2],[5] The lifetime risk of gonadal tumors is in range of 15–35%.
Histologically, GCTs are classified as germinomas, embryonic carcinomas, yolk sack tumors, malignant mixed GCTs and malignant teratomas. (7)
Malignant teratomas are only seen in neonates and infants.
Moreover, there were no cases of malignant teratomas, choriocarcinoma or other rarer tumours during the study period.

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