Testicular tumors can be classified according to etiology and morphology. 1. Etiological classification: it can be divided into two categories: primary and secondary. Primary testicular tumors are subdivided into testicular germ cell tumors and testicular non-germ cell tumors. Testicular germ cell tumors mainly include spermatogonia, spermatoblastic spermatogonia, embryonal carcinoma, teratoma, chorionic epithelial carcinoma, yolk sac tumors, and spermatogonial tubule germ cell sarcoma of seven cell types. Non-germ cell tumors of the testis include mesenchymal stromal cell tumors and supporting cell tumors. Secondary testicular tumors are mainly from reticuloendothelial tissue tumors and metastatic tumors such as leukemia, such as leukemic testicular tumors, microscopically visible leukemic cells infiltrated within the testicular interstitium. Testicular tumor can be a single tissue type, and more than half of them are mixed tumors of multiple tissue types. 2. Morphological classification: usually according to the cellular morphology, testicular tumors can be divided into spermatogonial tumors, non-spermatogonial germ cell tumors (including embryonal carcinoma, yolk sac tumors, teratomas, choriocarcinomas). However, it is not excluded that it is difficult to distinguish morphologically, and immunohistochemistry is valuable for the diagnosis and differential diagnosis of various types of testicular (ovarian) germ cells.