Testicular tumors account for 1-2% of all pediatric tumors, with an incidence of 0.05-2 per 100,000 children.  A bimodal age distribution is observed; one peak occurs in the first 2 years of life, and the second occurs in young adulthood.
Pediatric prepubertal testicular tumors are dramatically different from adult neoplasms. Germ-cell tumors account for only 60-77% of testicular tumors in children but account for 95% of testicular tumors in adults.  Adult germ-cell tumors with malignant potential, such as seminoma and embryonal carcinoma, are not present in prepubertal patients. Teratomas, which are uniformly benign in children, are often malignant in adults.
The most common germ-cell tumors are teratomas and yolk-sac tumors, which account for about 62% and 26% of testis tumors, respectively. [3, 4] Some series report that teratomas, which most believe are vastly underreported because of their benign nature, may account for almost 50% of prepubertal testicular tumors. However, in tumor registries, yolk-sac tumors are more common than teratomas, perhaps reflecting a reporting bias. [3, 5] Gonadal stromal tumors are significantly less common than germ-cell tumors (ie, tumors of non–germ-cell origin) and primarily include juvenile granulosa-cell tumors, Leydig-cell tumors, and Sertoli-cell tumors.
The vast majority (85%) of yolk-sac tumors in children present as clinical stage I disease, compared with only 35% in adults.  Alpha-fetoprotein (AFP) can be used as a reliable tumor marker because levels are increased in more than 90% of yolk-sac tumors. Therefore, patients can be safely managed with observation after orchiectomy followed by chemotherapy for recurrent tumors.  Retroperitoneal lymph node dissection is reserved for children with persistent retroperitoneal lymphadenopathy or increased serum tumor markers after orchiectomy and chemotherapy.
Prepubertal teratomas account for less than 30% of testicular germ-cell tumors in children and are uniformly benign.  Histology is often pure with diploid DNA content containing all 3 embryological germ layers (ectoderm, mesoderm, and endoderm). Testis-sparing surgery with frozen section is a reasonable consideration for this and other benign prepubertal tumors. No follow-up is recommended for prepubertal teratomas, whereas postpubertal patients should be monitored into adulthood.
Epidermoid cysts are benign tumors of epithelial origin and account for 10-15% of cases. [1, 8] They are often firm and well-defined, with a central hypoechoic region or mixed internal echogenicity surrounded by an echogenic rim on ultrasonography. Following tumor enucleation, these tumors do not require follow-up.
Seminomas and mixed germ-cell tumors are extremely rare in prepubertal children. Most authorities believe that seminomas should be managed as in adults and mixed germ-cell tumors should be treated based on the most malignant subtype.
Sertoli-cell tumors are the most common gonadal stromal tumors in prepubertal children. These tumors tend to appear as painless masses in boys younger than 6 months and produce no endocrinologic effects; however, 14% of patients present with gynecomastia.  All reported lesions in children younger than 5 years have been benign. Therefore, children younger than 5 years are adequately treated with orchiectomy and do not require metastatic evaluation. Older children should undergo chest radiography and abdominal CT scanning to rule out metastases. Metastases are treated with a combination of radiotherapy, chemotherapy, and retroperitoneal lymph node dissection. Large-cell calcifying Sertoli-cell tumor is a variant with large amounts of cytoplasm and calcification. One third of patients with this tumor have associated genetic abnormalities; however, these tumors are universally benign.
Leydig-cell tumors are the second most common gonadal stromal tumors in children and are also benign. These tumors most often occur in boys aged 5-10 years, and the synthesis of testosterone may produce precocious puberty, gynecomastia, and elevated levels of 17-ketosteroids. Leydig-cell tumors must be differentiated from hyperplastic nodules that develop in boys with poorly controlled congenital adrenal hyperplasia (CAH).
Juvenile granulosa-cell tumors account for approximately 3% of all neonatal testicular tumors and commonly appear as cystic, painless testicular masses. [7, 9, 10] They almost always appear in the first year of life, and most appear by age 6 months. They can be associated with anomalies of the Y chromosome, mosaicism, and ambiguous genitalia. These tumors are hormonally inactive and benign.
Gonadoblastoma occurs in association with disorders of sexual development (intersex). About 80% of cases involve phenotypic females with intra-abdominal testes or streak gonads.  The putative gonadoblastoma gene is on the Y chromosome, and the tumor almost always develops in a child with a Y chromosome. The streak gonads in patients with mixed gonadal dysgenesis often develop gonadoblastomas. The incidence peaks at puberty, and early gonadectomy is recommended in patients at risk for gonadoblastoma. Metastatic spread of a gonadoblastoma occurs in 10% of patients.  These tumors may elevate serum levels of beta-human chorionic gonadotropin (beta-HCG).
Cystic dysplasia of the testis is a benign lesion that is often associated with ipsilateral renal agenesis or dysplasia. This association, along with a characteristic ultrasonographic appearance (ie, hypoechoic lesions), permits preoperative diagnosis and possible treatment with testicular-sparing surgery. 
Leukemia and lymphoma are the most common secondary malignancies to affect the testis.  These tumors can present bilaterally, and, because the blood-testis barrier protects the intratesticular cells, the testis may be the site of residual tumor in children after chemotherapy. Metastatic disease to the testes should be considered in a child presenting with bilateral testicular tumors.
Paratesticular structures can give rise to various benign (lipoma, leiomyoma, hemangioma, or fibroma) and malignant tumors; however, these are extremely rare. Rhabdomyosarcoma is the most common malignant tumor (17%) and may arise from the distal spermatic cord and appear as a scrotal mass or hydrocele.  These tumors have a bimodal distribution and occur in boys aged 3-4 months and in teenagers. Up to 70% of cases involve the retroperitoneal lymph nodes at presentation.
These tumors are highly aggressive and spread via the blood, lymphatics, or direct extension to the lungs, the cortical bone, or to the bone marrow in 20% of patients at the time of diagnosis. Radical inguinal orchiectomy followed by retroperitoneal lymph node dissection is recommended for all children older than 10 years for those younger than 10 years with retroperitoneal disease. Patients with positive lymph nodes are treated with multimodal therapy (chemotherapy and radiation).
The testes are the affected organs.
Testicular tumors account for approximately 1-2% of all pediatric solid tumors.  The incidence is 0.05-2 per 100,000 children. Although benign tumors are more common in prepubertal patients than in postpubertal patients, yolk-sac tumors have been more commonly reported in some series and tumor registries. The true incidence of benign tumors, such as teratomas, may be less than what is reported because of reporting bias.
The worldwide incidence of prepubertal testicular and paratesticular tumors is similar to that in the United States.
One death occurs per every 10 million cases per year.
Testicular gem cell tumors appear to have a 1.4-fold greater incidence in Asian/Pacific Islanders than in white or black children. There seems to be no discernible difference in the incidence of testicular tumors between black and white boys aged 0-14 years. 
Testicular tumors occur in boys and men.
The incidence of pediatric testicular tumors peaks in children aged 2-4 years. Most yolk-sac tumors occur in children younger than 2 years.
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