Germ Cell Seminoma

Excerpt

Germ cell tumors (GCT), derived from primordial germ cells, are a diverse group of neoplasms that arise in the gonads (testicles and ovaries) primarily and may also arise in the anterior mediastinum, pineal gland, and brain. They are clinically classified into two major categories, with significant clinical and prognostic implications: Seminomas and non-seminomas. Seminomas generally have a good prognosis, while non-seminomatous tumors are much more likely to present with metastatic disease as well as mixed germ cell tumors comprising of two or more than two different germ cell tumor components. Although rare, GCT may also arise from extragonadal sites. Term “extragonadal germ cell tumor” (EGGCT) is implied in the absence of any primary gonadal neoplasm and represent 1% to 3% of all GCT. Seminoma constitutes 60% of all primary extragonadal GCT and is seen most notably in midline locations of the body like anterior mediastinum, central nervous system, and retroperitoneum. Seminoma in the retroperitoneum is generally metastatic disease from primary gonadal seminoma unless proven otherwise. In the central nervous system, the pineal gland and suprasellar regions are involved more frequently. Germinoma, an intracranial counterpart of seminoma (extragonadal seminoma), comprises approximately two-third of all intracranial GCT.

Germinoma can be pure or mixed (coexisting with other GCT, classified as non-germinomatous GCT). Non-germinomatous GCT makes up the remaining one third, including embryonal carcinoma, yolk sac tumor, choriocarcinomas, teratomas, and mixed tumors (containing more than one histologic element). Less commonly involved sites include paraventricular regions of basal ganglia and thalamus. Very rarely, synchronous involvement of the pineal and the suprasellar region is observed, called bifocal germinoma. Germinoma is more common in young adolescents and is usually diagnosed in the second decade of life. The prognosis is good, with a 5-year survival rate greater than 90% since the tumor is highly radiosensitive.