Germ cell tumor (GCT) is a neoplasm derived from germ cells. Germ-cell tumors can be cancerous or benign. Germ cells normally occur inside the gonads (ovary and testis). GCTs that originate outside the gonads may be birth defects resulting from errors during development of the embryo. Classification
GCTs are classified by their histology, regardless of location in the body. However, as more information about the genetics of these tumors become available, they may be classified based on specific gene mutations that characterize specific tumors. They 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 (around 25 years versus 35 years, in the case of testicular cancers), and have a lower five-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. Germinomatous
Nongerminomatous
Mixed
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.
Amish lethal microcephaly is a rare genetic disorder which is characterized by severe microcephaly (small head) from birth, brain hypoplasia (underdeveloped brain), micrognathia (small chin), irritability (at second or third month of age), seizures, problems controlling their body temperature, high levels of alpha-ketogluraic acid in their urine, and less commonly hepatomegaly (large liver). Babies with this condition typically die when they are 6 months old. This disorder was named after the Amish since, in Old Order Amish communities in Pennsylvania, it affects 1 in 500 babies, while 1 in 11 people in the same communities are unaffected carriers of the (recessive) mutation that causes the disorder, it has not been found outside this population.This disorder is caused by mutations in the SLC25A19 gene in chromosome 17q25, it follows an autosomal recessive inheritance pattern


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