Version July 2025
| Tumor type | Definition |
| Germinoma | A malignant germ cell tumor composed of cells resembling primordial germ cells |
| Mature teratoma | A germ cell tumor composed solely of fully differentiated, adult-type somatic tissue components that recapitulate the differentiating potential of the ectoderm, endoderm, and mesoderm |
| Immature teratoma | A germ cell tumor containing incompletely differentiated, fetal-like somatic tissue components that recapitulate the differentiating potential of the ectoderm, endoderm, and mesoderm; mature elements may be admixed |
| Teratoma with somatic-type malignancy | A germ cell tumor of mature or immature teratomatous type that develops a distinct secondary component resembling a somatic-type malignant neoplasm (eg, sarcoma or carcinoma) as seen in other organs and tissues |
| Embryonal carcinoma | A malignant germ cell tumor composed of large epithelioid cells resembling those of the embryonic germ disc |
| Yolk sac tumor | A malignant germ cell tumor that differentiates to resemble extraembryonic structures, including the yolk sac, allantois, and extraembryonic mesenchyme |
| Choriocarcinoma | A malignant germ cell tumor that differentiates to resemble the trophoblastic cells of the extraembryonic chorion, including syncytiotrophoblastic and cytotrophoblastic elements |
| Mixed germ cell tumors | Malignant germ cell tumors harboring at least 2 germ cell tumor subtypes in any combination |
