ARAS

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. The most notable of these is sacrococcygeal teratoma, the single most common tumor diagnosed in babies at birth.

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 sominoma.
• 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
• inside the cranium - pineal and suprasellar locations are most commonly reported

• 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
  Main article: Ovarian cancer
• testis
  Main article: Testicular cancer

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.

Males 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.

A small study of ovarian tumors in girls reports a correlation between cystic and benign tumors and, conversely, solid and malignant tumors. Because the cystic extent of a tumor can be estimated by ultrasound, MRI, or CT scan before surgery, this permits selection of the most appropriate surgical plan to minimize risk of spillage of a malignant tumor.

Access to appropriate treatment has a large effect on outcome. A 1993 study of outcomes in Scotland found that for 454 men with non-seminomatous (non-germinomatous) germ cell tumors diagnosed between 1975 and 1989, 5-year survival increased over time and with earlier diagnosis. Adjusting for these and other factors, survival was 60% higher for men treated in a cancer unit that treated the majority of these men, even though the unit treated more men with the worst prognosis.