Yolk sac tumor after post-detorsion changes in a torsed undescended testis: a case report

Cryptorchidism complicated by testicular torsion is an uncommon but clinically important emergency in pediatric urology. Cryptorchidism is also a recognized risk factor for testicular germ-cell tumors. However, malignancy arising or becoming clinically apparent after testis-sparing detorsion in a torsed undescended testis is rarely reported. In particular, postoperative heterogeneous parenchymal echogenicity is often interpreted as benign post-ischemic change, which may reduce vigilance for occult malignancy.

We report the case of a 2-year-5-month-old boy who underwent emergency detorsion and orchiopexy for a 720° clockwise torsion of a right undescended testis. Preoperative ultrasonography demonstrated heterogeneous echogenicity and absent blood flow, consistent with torsion. After detorsion, the testis was preserved at the family's request. Early postoperative ultrasonography showed heterogeneous parenchymal changes with reduced focal perfusion, which were interpreted as postoperative changes. Follow-up ultrasonography at 1, 3, and 5 months demonstrated preserved perfusion without a definable mass. Approximately 6 months after surgery, the child developed progressive right scrotal enlargement. Repeat ultrasonography and magnetic resonance imaging suggested a right scrotal tumor, and serum alpha-fetoprotein was markedly elevated at 1,258.7 ng/mL, while beta-human chorionic gonadotropin remained normal. Radical orchiectomy was performed, and final histopathology confirmed a yolk sac tumor. Postoperatively, alpha-fetoprotein declined rapidly to the normal range, and no recurrence or metastasis was detected during short-term follow-up.

This case highlights that malignancy may become clinically apparent after testis-sparing detorsion in a cryptorchid testis. In high-risk settings such as cryptorchidism, postoperative follow-up should assess not only reperfusion but also dynamic morphologic evolution. Progressive enlargement, development of a definable solid lesion, or atypical vascularity should prompt timely tumor marker evaluation and further imaging to avoid delayed diagnosis of malignancy.