Testicular tumors account for 5%-9% of genital tumors in the male urinary tract and 1%-2% of whole body tumors in men. Germ cell tumors account for 90-95% of testicular tumors, and bilateral testicular tumors account for 1%-2%. In the past 40 years, the incidence of testicular tumors has increased 1-fold worldwide. However, there are obvious regional and racial differences in the incidence of testicular tumors. The higher rates are in Denmark, Norway, Switzerland, Germany and New Zealand; the United States is slightly lower at 3.7/100,000, and the incidence rate of whites is 4 times that of blacks; the incidence rates in Asia and Africa are the lowest, and the incidence rate of testicular tumors in China is about 1 per 100,000. While in Israel, the incidence rate of Jews is more than 8 times higher than that of non-Jews. The peak age of testicular tumor incidence is 20-40 years old, and its common pathological types vary in different age groups. Yolk sac tumor is the most common before puberty, embryonal carcinoma occurs mostly in young adults, and seminoma is seen in 20-50 years old. With the improvement of diagnostic techniques, the application of combined chemotherapy and the improvement of surgical methods, the cure rate of testicular tumors has increased to 90%~95% in the past 40 years; especially the treatment of testicular germ cell tumors is a good example of successful comprehensive treatment. Etiology and pathogenesis The etiology of testicular tumors is not well understood. It is related to genetic, viral infection, and testicular trauma, but all of them lack sufficient evidence. Cryptorchidism is the first relevant factor for its development. 5%-20% of patients have previous history of cryptorchidism, and the malignant rate of cryptorchidism is 20-40 times higher than normal people, and the malignant rate of intra-abdominal cryptorchidism is 4 times higher than that of inguinal cryptorchidism. The causes of testicular tumor in cryptorchidism include abnormal germ cells, elevated local temperature, gonadal insufficiency and endocrine dysfunction, etc. The chance of testicular tumor can be reduced by repositioning and fixing cryptorchidism before the age of 10. The World Health Organization (WHO) classified testicular tumors into germ cell tumor (GCT), gonadal/interstitial tumor and other non-specific interstitial tumors according to their morphology, growth pattern and plasma tumor markers in 2004. GCT is divided into two major types: SGCT (classic seminoma) and NSGCT (non-seminomatous seminoma); NGCT (embryonal carcinoma, teratoma, choriocarcinoma and yolk sac tumor). The four basic forms of NGCT are embryonal carcinoma, teratoma, epithelial carcinoma and yolk sac tumor. According to the tissue type contained in the tumor, it can be divided into single tissue type and mixed type of two or more tissues. 40% of testicular tumors are mixed type of two or more tissue types. Mixed tumors are relatively common in adults, while children tend to have a single component.