Objectives  To investigate the clinicopathologic characteristics, immunohistochemistry, therapy, and prognosis of testicular yolk sac tumors in infants.

  Methods  The clinicopathologic data of 11 cases of testicular yolk sac tumors were analyzed.In addition, the morphological characteristics and immunohistochemisty of the tumor cells were observed among the yolk sac tumor cases, including Glypican-3, AFP, CK8 & 18, HCG, PLAP, CD99, S-100, and CD34 markers.

  Results  The median age was 15 months in all tumor cases, and the right testicular tumor ranked the first(9/11).The most common presenting symptom was gradual and painless enlargement in the single-sided testis.The serum AFP level was significantly elevated in yolk sac tumors.Classified by pathological tissue, these cases were classified by pathological tissue into 10 pure yolk sac tumors and 1 yolk sac tumor mixed with mature teratoma element.On immunostaining, Glypican-3 provided the most intense and diffuse reactivity for all yolk sac tumors.In contrast, CK8 & 18 and a-fetoprotein were variably positive, whereas CD99, S-100, and CD34 were uniformly negative.Eleven cases were treated with complete excision, and two cases with intravascular tumor emboli in the peritumoral tissue underwent auxiliary chemotherapy.Follow-up revealed that all children are surviving well without any signs of recurrence or metastasis.

  Conclusion  Pure yolk sac tumor is the most common testicular germ cell tumor in children younger than 3 years, and mixed yolk sac tumor is very rare.Glypican-3 is a new, specific, and sensitive diagnostic antibody for yolk sac tumor.High ligation and spermatic testicular resection of the infant testis yolk sac tumor result in good prognosis, and adjuvant chemotherapy for high-risk children has been shown to be manageable.