Sentinel Lymph Node Biopsy in Stage AI-IIA Germ Cell Tumors

Inclusion Criteria: * Male person at least 18 years of age at the time of signing the informed consent form; * Provisional diagnosis of testicular tumor with isolated retroperitoneal lymphadenopathy; * Computed tomography data of the abdominal cavity and retroperitoneal space with axial visualization of lymphadenopathy (within 6 weeks before the planned date of surgical treatment): at least one lymph node larger than 1 cm. Exclusion Criteria: * Severe or uncontrolled concomitant chronic diseases or acute diseases; * Any condition that, in the opinion of the physician, may limit compliance with the study; * Poor general condition (ECOG \> 2, KPS \< 70); * Refusal of the patient to comply with the study procedures or refusal of the patient to continue participating in the study; * Development of diseases or conditions that prevent the patient's continued participation in the study; * AFP level is higher than reference values and / or b-hCG \> 100 mIU/ml; * Presence of a second malignant disease; * History of systemic antitumor therapy and/or radiotherapy; * Inadequate bone marrow, liver, kidney function: (Neutrophils \< 1.5 x 10\^9/l, Platelets \< 100 x 10\^9/l, ALT \> 3 x ULN, AST \> 3 x ULN, Total bilirubin \> 1.5 xULN, GFR \<35 ml/min)