Germ cell tumors are abnormal cell proliferations that occur in the gonads or outside the gonads (in areas related to their embryonic development). During embryonic development, germ cells pass from the yolk sac through the mesentery and finally descend to the pelvic cavity or scrotum to form the G-pill or ovary. Therefore, germ cell tumors not only occur in the G-pill or ovary, but also in areas outside the gonads, such as the posterior abdominal cavity, the caudal vertebrae, the mediastinal cavity or the central nervous system, etc. In children, 70 germ cell tumors occur outside the gonads, and teratomas of the caudal sacral vertebrae are the most common ones. Common germ cell tumors: 1. Teratoma (teratoma) If the diagnosis is more than two months old, the chance of malignancy is up to more than half, therefore, surgical resection must be done as early as possible; if it is malignant, chemotherapy and radiation therapy should be added. From age one to puberty, it is most common in the brain, neck, anterior mediastinum, abdomen or pelvic cavity. After puberty, they are more common in the gonads. Germinoma may occur in the gonads or outside the gonads. Germinomas that grow in the G-pill are also called seminomas, and those that grow in the ovary are also called dysgerminomas. Generally speaking, the prognosis of dysgerminoma is good, and it is quite sensitive to radiation. For example, for dysgerminoma of the ovary, the survival rate of ten years after surgery is as high as more than 85%. Yolk sac tumor is the most common malignant germ cell tumor in children, and its most common site is cauda equina area, followed by G-pill and ovary. For yolk sac tumors growing in the G-pill, if the child is younger than one year old and has not metastasized, surgical removal of the G-pill is usually sufficient; if the child is older than one year old, the prognosis is poorer, and chemotherapy and radiation therapy must be added. Yolk sac tumor of ovary usually grows rapidly and is easy to metastasize. In addition to removing the affected fallopian tube and ovary, chemotherapy or radiation therapy should be added to the treatment. Some tumors do not need other treatments after surgery, while some tumors need to be treated with radiation or chemotherapy. Some malignant germ cell tumors are very likely to metastasize to lymphatic or distant places, so chemotherapy must be added. Chemotherapy is the use of chemicals to destroy tumor cells or slow down their growth, and the drugs are usually given by intravenous injection. Radiation therapy is mainly for the treatment of intracranial tumors or metastatic tumors. Testicular tumors in children should be considered as malignant tumors, which should be explored by inguinal incision, firstly ligating the spermatic cord at the inner ring to block the spermatic cord, exploring the testis, and then radical orchiectomy should be performed for those who are diagnosed as tumors by biopsy and frozen section. Malignant tumors are treated according to clinical stage. Stage I cases are treated with chemotherapy for 1 year after radical orchiectomy. stage I testicular malignant tumors in infants less than 1 year of age are not treated with chemotherapy and are followed up regularly. In stage II cases, after radical orchiectomy, the scope of surgical resection was decided according to the extent of malignant tumor infiltration and lymph node metastasis. generally, only inguinal lymph node dissection was performed in stage IIa, and retroperitoneal lymph node dissection was performed only when serum AFP was still elevated in two weeks after the operation and abdominal lymph node enlargement was confirmed by CT, and retroperitoneal lymph node dissection was performed routinely in stage II b. In stage II, chemotherapy was given for 2 years after operation, and chemotherapy was not allowed in stage I infants within 1 year. Postoperative chemotherapy was administered for 2 years. In stage III cases, after radical orchiectomy, those with residual tumor and extensive metastasis should be treated with local radiotherapy, and isolated lung and liver metastatic lesions should be treated with surgical resection, and postoperative chemotherapy with multi-drug combination of cisplatin, VP-16, bleomycin, and isocyclophosphamide should be carried out for 2 years. Prognosis: Benign testicular tumors can survive for a long time without recurrence after radical surgery. The overall survival rate of pediatric testicular malignant tumors is 60-80%, infant testicular embryonal adenocarcinoma and epididymal rhabdomyosarcoma have a better prognosis, with the survival rate reaching 75% and 71%, respectively, and the survival rate of yolk sac tumor and malignant teratoma can also reach 50% after comprehensive treatment.The near-term therapeutic efficacy of the stage I and II cases can be up to 100%, but the survival rate of those who had relapsed after the operation is only 15%. However, the survival rate of postoperative recurrence is only 15%, and the prognosis of stage III is poorer. Regular measurement of tumor markers after surgery can detect recurrence cases at an early stage. Endodermal sinus tumor of ovary, also known as yolk sac tumor, is the third most common malignant germ cell tumor of ovary, and the first common malignant germ cell tumor of ovary in China, which may be related to the difference of pathological diagnostic criteria. Endodermal sinus tumors have the worst prognosis among malignant germ cell tumors of the ovary.Ayhan 1995 reported 76 cases of malignant germ cell tumors of the ovary, with an overall 5-year survival rate of 60.6%, compared to 12.O% for endodermal sinus tumors. Endodermal sinus tumors occur at an average age of 18-19 years. Due to the rapid growth of the tumor and easy to have rupture of the peritoneum and abdominal implantation, the common symptoms include abdominal mass, abdominal distension, abdominal pain and ascites, and often due to the tumor is huge (10-40cm in diameter), hemorrhage, necrosis and cystic degeneration and lead to increased body temperature. Some patients had Maggot’s syndrome and endocrine disorders caused by tumor paracrine (such as hyperthyroidism), and the ovarian function of the patients was generally normal. Endodermal sinus tumors are highly malignant, so most patients have pelvic and abdominal metastases at the time of presentation, and the rate of lymph node metastasis can be as high as 20% (Gershenson 1983). Most endodermal sinus tumors can synthesize AFP, and serum AFP testing can be useful for definitive diagnosis, and there is a high correlation between the extent of the lesion and the serum AFP level. Endodermal sinus tumors are often associated with other types of germ cell tumors; pure-type endodermal sinus tumors secrete only AFP, while mixed endodermal sinus tumors may also show elevated serum HCG (including choriocarcinomas), and serum levels of these markers (especially AFP) are useful for monitoring the efficacy of treatment.