Germ cell tumor

Germ cell tumor (GCT) is a tumor (neoplasm) derived from germ cells. (Germ cells themselves are not pathogenic; i.e., they are not the viral and bacterial "germs" that cause illness.) Germ cell tumors can occur both inside and outside of the gonads (ovary and testis).

 Etiology 

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 germ cell tumors were thought initially to be isolated metastases from an undetected primary tumor in a gonad, but it is now known that many germ cell tumors are congenital and originate outside the gonads.

Classification

Germ cell tumors are classified by their histology, regardless of location in the body.

 Germ cell tumors are broadly divided in two classes. The germinomatous or seminomatous germ cell tumors (GGCT, SGCT) include only germinoma and its synonyms dysgerminoma and seminoma. The nongerminomatous or nonseminomatous germ cell tumors (NGGCT, NSGCT) include all other germ cell 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.

Location

 Despite their name, germ cell tumors occur both within and outside the ovary and testis.

     * head

          o inside the cranium — pineal and suprasellar locations are most commonly reported

          o inside the mouth — a fairly common location for teratoma

    * neck

    * 1% to 5% in the mediastinum (mediastinal germ cell tumor)

    * pelvis, particularly sacrococcygeal teratoma

 ·          ovary 

In females, germ cell tumors account for 30% of ovarian tumors, but only 1 to 3% of ovarian cancers in North America. In younger women germ cell tumors are more common, thus in patients under the age of 21, 60% of ovarian tumors are of the germ cell type, and up to one-third are malignant. In males, germ cell tumors of the testis occur typically after puberty and are malignant (testicular cancer). In neonates, infants, and children younger than 4 years, the majority of germ cell tumors are sacrococcygeal teratomas.

 Persons with Klinefelter's syndrome have a 50 times greater risk of germ cell tumors (GSTs). In these persons, GSTs usually contain nonseminomatous elements, present at an earlier age, and seldom are gonadal in location.

Prognosis

 The 1997 International Germ Cell Consensus Classification is a tool for estimating the risk of relapse after treatment of malignant germ cell tumor.