PURPOSEWe aimed to assess the relationship between gynecomastia and tumor markers, histologic subtypes, and prognosis in patients with testicular germ cell tumors.METHODSThis study included 73 testicular germ cell cancer patients with pretreatment chest, abdomenand pelvis computed tomography (CT) scans and tumor markers (β-human chorionic gonadotropin [β-hCG], lactate dehydrogenase [LDH], α-fetoprotein [AFP]). The volumetric analysis ofthe breast glandular tissue, the presence of gynecomastia and metastatic disease were determined using CT scans. Patients were classified according to the International Germ Cell CancerCollaborative Group (IGCCCG) prognostic classification. The association between gynecomastia,breast glandular tissue volume, tumor markers, metastatic disease, and disease prognosis wereevaluated.RESULTSThirty-four of the patients (46.6%) had gynecomastia. A breast volume cutoff value of 0.78 cm3to diagnose gynecomastia led to 85% sensitivity and 95% specificity. Serum β-hCG level correlated with the breast glandular tissue volume weakly (r=0.242, P = 0.039). Gynecomastia wasmore common in patients with elevated β-hCG levels (P = 0.047), and was not associated withpulmonary, nonpulmonary distant, or nodal metastases (P = 0.378, P = 0.884, P = 0.333, respectively). No significant association was found between the disease prognosis and gynecomastia(P = 0.556).CONCLUSIONGynecomastia was common among testicular germ cell cancer patients with elevated β-hCG.However, it was not associated with metastatic disease and prognosis.