Germ Cell Tumor

A Germ Cell Tumor (GCT) is a neoplasm derived from germ cells. Germ cells normally occur inside the gonads (ovary and testis). Tumors that originate outside the gonads may be birth defects resulting from errors during development of the embryo.
Some investigators suggest that this distribution arises as a consequence of abnormal migration of germ cells during embryogenesis. Others hypothesize a widespread distribution of germ cells to multiple sites during normal embryogenesis, with these cells conveying genetic information or providing regulatory functions at somatic sites. Extragonadal tumors were thought initially to be isolated metastases from an undetected primary tumor in a gonad, but it is now known that many germ cells are congenital and originate outside the gonads. The most notable of these is sacrococcygeal teratoma, the single most common tumor diagnosed in babies at birth.
Tumors are broadly divided in two classes: The germinomatous or seminomatous(GGCT, SGCT) include only germinoma and its synonyms dysgerminoma and seminoma. The nongerminomatous or nonseminomatous germ cell tumors (NGGCT, NSGCT)include all other germ tumors, pure and mixed. The two classes reflect an important clinical difference. Compared to germinomatous tumors, nongerminomatous tumors tend to grow faster, have an earlier mean age at time of diagnosis (~25 years versus ~35 years, in the case of testicular cancers), and have a lower 5 year survival rate. The survival rate for germinomatous tumors is higher in part because these tumors are exquisitely sensitive to radiation, and they also respond well to chemotherapy. The prognosis for nongerminomatous has improved dramatically, however, due to the use of platinum-based chemotherapy regimens. Teratocarcinoma is an old name for a tumor that is a mixture of teratoma and embryonal carcinoma. In more modern usage, this kind of mixed germ cell may be known as a teratoma with elements of embryonal carcinoma, or simply as an embryonal carcinoma.

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