Teratoma

A tumor containing mature or immature tissues derived from one or more embryonic germ layers. Teratomas arise from germ cells or, less commonly, embryonic cells.

Germ cell: A reproductive cell that gives rise to eggs or sperm. Teratomas commonly originate from germ cells that retain the capacity to form diverse tissues.
Germ cell development: The formation, migration, and maturation of cells that produce eggs or sperm. Errors in germ-cell development can leave cells in unusual locations or developmental states.
Sacrococcygeal teratoma: A teratoma arising near the tailbone, most often diagnosed in newborns and infants. This is the most common teratoma in infancy and a classic congenital presentation.
Histopathology: The microscopic examination of diseased tissue to establish diagnosis and characterize lesions. Tissue sampling distinguishes mature from immature components and identifies malignant transformation.
Teratoma syndrome: A complication in which mature teratoma grows during or after chemotherapy for a nonseminomatous germ-cell tumor. Its chemotherapy-resistant growth raises questions about tumor differentiation and treatment timing.
Embryonic germ layer: One of the primary cell layers formed during early embryonic development: ectoderm, mesoderm, or endoderm. Teratoma tissues can represent derivatives of multiple embryonic layers.
Primordial germ cell: An embryonic precursor cell that migrates to the developing gonad and later forms gametes. Misplaced primordial germ cells are one proposed source of extragonadal teratomas.
Ovarian teratoma: A teratoma arising in an ovary, commonly a mature cystic teratoma called a dermoid cyst. Ovarian teratomas are a frequent presentation in reproductive-age patients.
Alpha-fetoprotein: A fetal protein measured in blood and used as a marker in several cancers and pregnancy assessments. Elevated levels can signal yolk-sac tumor elements within a germ-cell tumor.
Growing teratoma syndrome: Enlargement of a mature teratoma during or after chemotherapy while tumor markers normalize. This defined pattern distinguishes persistent mature tissue from chemotherapy-resistant malignant disease.

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