Many diseases can infiltrate the testis, one of the more typical ones being leukemic testicular infiltration, in which leukemic cancer cells mainly infiltrate the testicular mesenchyme and destroy the varicocele. Leukemic testis is often secondary to leukemia in children with acute lymphoblastic leukemia, with a rate of involvement of up to 8%, and in fact the incidence of leukemia involving the testis is even higher. What tests do we need to do when the testes are infiltrated? 1. Ultrasound or CT examination may reveal infiltration of the testis. 2, Testicular leukemia can have no early manifestations and is only found on testicular biopsy. Patients with obvious testicular leukemia show painless enlargement, local hardening, and can be nodular, with changes in scrotal skin color, mostly brown-black or green-black, and negative transillumination test. 3. Most testicular swellings are unilateral, but can also be bilateral. Even if the swelling is unilateral, the other side usually has subclinical microscopic changes. Thus, testicular leukomalacia actually often invades both testes. In addition, a small number of patients may have testicular enlargement with swelling and pain and a feeling of downward movement. 4. The early diagnosis of testicular leukemia is difficult. In patients with acute leukemia, especially in children with acute lymphoblastic leukemia, the diagnosis can be confirmed when testicular enlargement is present, such as pathological confirmation of leukemic cell infiltration. If tissue examination fails, terminal deoxynucleotidyl transferase staining and electron microscopy can be used, which is helpful in the diagnosis of some microscopic testicular infiltrative foci.