A 31-year-old male patient, with no relevant personal medical history, who comes to his primary care physician reporting having noticed a lump in his left testicle for the past 3 weeks. No local pain, no urinary symptoms, no prostatic syndrome, no fever, no weight loss. His family physician  discover after on physical examination, a large, hard mass is palpable in the left testicle. No inguinal lymph nodes are palpable. An ultrasound performed in primary care detected a large homogeneous and hypoechoic mass that occupies almost the total left testicle. A body CT scan was performed, which did not show distant metastatic disease A left orchiectomy was performed, and the anatomopathological study revealed a testicular seminoma.       ..Seminoma is a malignant germ cell tumor of the testis, accounting for approximately half of all testicuLar germ cell tumors. It typically presents as a unilateral testicular mass in men aged 30-40 years, and its high sensity to radiotherapy and chemotherapy, with an excellent long-term survival rate.   Diagnosis is established by physical examination of the testes and scrotal ultrasonography showing an homogeneously hypoechoic intratesticular mass, and confirmed by histopathology following radical inguinal orchiectomy. Pure seminoma does not elevate Alpha fetoprotein. B-human chorionic gonadotropin may be midly elevated in up to 30% of cases. Scrotal ultrasound has a sensitive and specificity > 90% for distinguishing malignant from benign massesStaging with computed tomography of the chest, abdomen and pelvis is recommended to assess for metastatic diseasee. Radical inguinal orchiectomy is both diagnostic and therapeutic. Histopathological assessment of the orchiectomy specimen confirms seminoma. Percutaneous biopsy is contraindicated due to risk of tumor seeding.A seminoma should be suspected in any male, typically aged 30-40 years, , presenting with a painless, unilateral testicular mass, or with extratesticular symptoms such as abdominal mass, gynecomastia, or supraclevicular lymphadenopathy, especially if risk factors like cryptorchidism or family history of testicular cancer are present.