Paratesticular rhabdomyosarcoma (RMS) is an uncommon pediatric soft tissue malignancy that arises from mesenchymal elements of the spermatic cord, epididymis, or surrounding scrotal tissues. It often presents as a painless scrotal mass and may resemble benign conditions such as hydrocele or epididymitis, leading to delayed diagnosis. Although rare, it constitutes a significant portion of pediatric genitourinary sarcomas. Early recognition is vital, as paratesticular RMS has a propensity for rapid lymphatic spread, particularly to pelvic and retroperitoneal nodes. Diagnosis relies on imaging, histopathology, and immunohistochemistry, while treatment generally involves radical orchiectomy followed by chemotherapy based on risk stratification. We report a pediatric case with early lymphatic dissemination requiring prompt multimodal intervention.

Clinical data were obtained from medical records of a 12-year-old male patient diagnosed with paratesticular RMS. Evaluations included physical examination, laboratory studies (tumor markers), imaging (CT and PET), surgical pathology, and immunohistochemistry. Treatment followed the Taiwan Pediatric Oncology Group (TPOG) RMS-2016 intermediate-risk protocol.

The patient presented with a one-month history of painless right scrotal swelling. A firm, non-tender mass was noted on examination. CT imaging demonstrated a right paratesticular mass. Tumor markers (AFP, β-hCG) were normal. An elective radical orchiectomy was initially planned but expedited due to sudden scrotal cyanosis suggestive of tumor rupture.

Histological analysis of the resected mass revealed embryonal RMS, measuring 6.6 cm, with negative margins and no lymphovascular invasion. Immunohistochemical staining supported the diagnosis (WT1, Myogenin, MyoD1, Desmin positive). PET-CT revealed FDG-avid lymphadenopathy in the right pelvic and paraaortic regions. The patient underwent Port-A catheter placement and initiation of chemotherapy per the TPOG RMS-2016 IR protocol. He tolerated induction therapy well and was discharged in stable condition.

This case underscores the importance of early detection and intervention in paratesticular RMS. Although the disease may appear localized initially, early metastatic spread through lymphatic pathways is not uncommon. Accurate staging and timely multimodal therapy are essential for favorable outcomes in pediatric patients with RMS.

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