Germ cell tumor

Germ cell tumor
Classification and external resources
Micrograph of a seminoma, a common germ cell tumor.
ICD-10	C56, C62, D27, D29.2
ICD-9	183, 186, 220, 222.0
ICD-O:	9060-9100
eMedicine	med/863
MeSH	D009373

A germ cell tumor (GCT) is a neoplasm derived from germ cells. Germ cell tumors can be cancerous or non-cancerous tumors. Germ cells normally occur inside the gonads (ovary and testis). Germ cell tumors that originate outside the gonads may be birth defects resulting from errors during development of the embryo.

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,^[1] regardless of location in the body.

Germ cell tumors are broadly divided in two classes:^[2]

• 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 very sensitive to radiation, and they also respond well to chemotherapy. The prognosis for nongerminomatous tumours has improved dramatically, however, due to the use of platinum-based chemotherapy regimens.^[3]

Germinomatous

Tumor	ICD-O	Peak Age (yr)	Benign or malignant	Histology	Tumor marker
Germinoma (including dysgerminoma and seminoma)		40–50	Malignant	Sheets of uniform polygonal cells with cleared cytoplasm; lymphocytes in the stroma	10% have elevated hCG
Dysgerminoma	M9061/3
Seminoma	M9060/3

Nongerminomatous

Tumor	ICD-O	Peak Age (yr)	Benign or malignant	Histology	Tumor marker
Embryonal carcinoma	9070/3	20–30	Malignant	Poorly differentiated, pleomorphic cells in cords, sheets, or papillary formation	Pure tumors do not secrete hCG, AFP
Endodermal sinus tumor, also known as yolk sac tumor (EST, YST)	9071/3	3	Malignant	Poorly differentiated endothelium-like, cuboidal, or columnar cells	100% secrete AFP
Choriocarcinoma	9100/3	20–30	Malignant	Cytotrophoblast and syncytiotrophoblast without villus formation	100% secrete hCG
Teratoma including mature teratoma, dermoid cyst, immature teratoma, teratoma with malignant transformation	9080/0-9080/3	0–3, 15–30	Mature teratoma, dermoid cyst usually benign (but follow-up required); others usually malignant	Very variable, but "normal" tissues are common	Pure tumors do not secrete hCG, AFP
Polyembryoma	9072/3	15–25	?	?	?
Gonadoblastoma	9073/1	?	?	?	?

Mixed

Tumor	ICD-O	Peak Age (yr)	Benign or malignant	Histology	Tumor marker
Mixed		15–30	Malignant	Depends on elements present	Depends on elements present

Mixed germ cell tumors occur in many forms. Among these, a common form is teratoma with endodermal sinus tumor.

Teratocarcinoma refers to a germ cell tumor that is a mixture of teratoma with embryonal carcinoma, or with choriocarcinoma, or with both.^[4] This kind of mixed germ cell tumor may be known simply as a teratoma with elements of embryonal carcinoma or choriocarcinoma, or simply by ignoring the teratoma component and referring only to its malignant component: embryonal carcinoma and/or choriocarcinoma. They can present in the anterior mediastinum.

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

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).^[5] 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^[6] is a tool for estimating the risk of relapse after treatment of malignant germ cell tumor.

A small study of ovarian tumors in girls^[7] 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.^[8]

Research

Germ cell tumors of children are the subject of clinical research by the worldwide Children's Oncology Group (COG), in a number of studies coordinated by Dr. John Cullen, MD.^[9]

Intracranial Germ Cell Tumors have been studied through the International CNS GCT Study Group. Under the direction of Jonathan Finlay, the program director, three international treatment studies have been initiated since 1990 with the goal to maintain a high rate of cure while minimizing the late effects of treatment.

See also

• Embryonic stem cells

References

External links

• humpath #2658 (Pathology images)
• Childhood Extracranial Germ Cell Tumors
• Extragonadal Germ Cell Tumors
• Ovarian Germ Cell Tumors
• Primary Germ Cell Tumors of the Thorax
• Malignant Mediastinal Germ Cell Tumors
• Packer RJ, Cohen BH, Cooney K, Coney K (2000). "Intracranial germ cell tumors". Oncologist 5 (4): 312–20. PMID 10964999. http://theoncologist.alphamedpress.org/cgi/content/full/5/4/312#R9.