Malignant neoplasm of the testis, occurring most often in men between the ages of 20 and 35, often affecting an undescended testis and more frequently the right testis. In its early stages testicular cancer is often asymptomatic, and it may metastasize, later causing urinary and pulmonary symptoms and an abdominal mass. Treatment depends on the nature of the tumor and includes surgery (orchidectomy), radiation, and/ or chemotherapy.