teratoma
Pronunciation: tair-uh-TOH-muh
A germ cell tumour composed of tissues derived from more than one embryonic germ layer, occurring most frequently at sacrococcygeal, gonadal, or mediastinal sites in children.
Full Definition
Teratomas are neoplasms arising from pluripotent germ cells and containing elements of ectoderm, mesoderm, and/or endoderm in varying combinations. In the pediatric population, sacrococcygeal teratoma is the most common congenital solid tumour, classified by the Altman system (types I–IV) based on the ratio of external to presacral components. Mature teratomas contain well-differentiated tissues (e.g., skin, hair, teeth), whereas immature teratomas contain embryonic-type neuroepithelium graded 0–3. Malignant transformation to a yolk sac tumour or other germ cell element is possible. Editors should not conflate 'teratoma' with 'dermoid cyst', which is a restricted subtype, nor with the broader category 'germ cell tumour'.
Usage
Usage note: 'Teratoma' and 'dermoid cyst' are not interchangeable; a dermoid cyst is a mature cystic teratoma, but not all teratomas are dermoid cysts. Preserve the author's distinction.
In Context
- "Antenatal ultrasound detected a large sacrococcygeal teratoma with a predominantly external (Altman type I) component." — Fetal medicine report
- "The resection specimen contained mature and immature elements; grading of the immature teratoma was recorded as grade 2." — Neonatal surgical pathology report