descends vertically into the scrotum consists of vas deferens, testicular artery, cremasteric artery, deferential artery, pampiniform plexuses, genitofemoral nerve, and lymphatic vessel. Intratesticular tumors One of the primary indications for scrotal sonography is to evaluate for the presence of intratesticular tumor in the setting of scrotal enlargement or a palpable abnormality at physical examination. It is well known that the presence of a solitary intratesticular solid mass is highly suspicious for malignancy. Conversely, the vast majority of extratesticular lesions are benign. Germ cell tumors Primary intratesticular malignancy can be divided into germ cell tumors and non–germ cell tumors. Germ cell tumors are further categorized as either seminomas or nonseminomatous tumors. Other malignant testicular tumors include those of gonadal stromal origin, lymphoma, leukemia, and metastases. Seminoma Approximately 95% of malignant testicular tumors are germ cell tumors, of which seminoma is the most common. It accounts for 35%–50% of all germ cell tumors. Seminomas occur in a slightly older age group when compared with other nonseminomatous tumor, with a peak incidence in the fourth and fifth decades. They are less aggressive than other testicular tumors and usually confined within the tunica albuginea at presentation. Seminomas are associated with the best prognosis of the germ cell tumors because of their high sensitivity to radiation and chemotherapy. Seminoma is the most common tumor type in cryptorchid testes. The risk of developing a seminoma is increased in patients with cryptorchidism, even after orchiopexy. There is an increased incidence of malignancy developing in the contralateral testis too, hence sonography is sometimes used to screen for an occult tumor in the remaining testis. On US images, seminomas are generally uniformly hypoechoic, larger tumors may be more heterogeneous [Fig. 3]. Seminomas are usually confined by the tunica albuginea and rarely extend to peritesticular structures. Lymphatic spread to retroperitoneal lymph nodes and hematogenous metastases to lung, brain, or both are evident in about 25% of patients at the time of presentation. Nonseminomatous germ cell tumors Nonseminomatous germ cell tumors most often affect men in their third decades of life. Histologically, the presence of any nonseminomatous cell types in a testicular germ cell tumor classifies it as a nonseminomatous tumor, even if most of the tumor cells belong to seminoma. These subtypes include yolk sac tumor, embryonal cell carcinoma, teratocarcinoma, teratoma, and choriocarcinoma. Clinically nonsemionatous tumors usually present as mixed germ cell tumors with various cell types and in different