METASTATIC PARATESTICULAR EMBRYONAL RHABDOMYOSARCOMA WITH DELAYED OSSEOUS RELAPSE IN AN ADOLESCENT: A CASE REPORT AND LITERATURE REVIEW

Paratesticular embryonal rhabdomyosarcoma (PT-RMS) is an uncommon pediatric soft-tissue sarcoma that typically presents as a painless scrotal or inguinal mass. We report a 15-year-old boy with a progressively enlarging painless right paratesticular mass and normal serum alpha-fetoprotein, beta-human chorionic gonadotropin, and lactate dehydrogenase levels. Doppler ultrasonography demonstrated a heterogeneous, hypervascular, 7.5-cm extratesticular lesion, while staging computed tomography (CT) identified retroperitoneal lymphadenopathy and bilateral pulmonary nodules. 
Core biopsies of the primary lesion and a retroperitoneal node showed embryonal rhabdomyosarcoma (ERMS) with myxoid stroma, rhabdomyoblasts, brisk mitotic activity, and strong myogenic immunophenotype (Desmin, MyoD1, and focal Myogenin). Molecular testing was negative for PAX3/7: FOXO1 fusions, supporting a fusion-negative molecular profile. Given metastatic disease at presentation, the multidisciplinary team prioritized tissue diagnosis and neoadjuvant high-risk chemotherapy over immediate definitive surgery. Marked radiologic regression after three cycles permitted radical inguinal orchiectomy, which showed extensive treatment effect with only microscopic residual viable tumors. Despite completion of chemotherapy and an 18-month disease-free interval, surveillance imaging at 22 months revealed biopsy-proven solitary iliac osseous relapse. 
This case illustrates that adolescent age, nodal and pulmonary dissemination, and later skeletal recurrence may outweigh the otherwise favorable implications of embryonal histology and fusion-negative status. It emphasizes early imaging, expert pathology, molecular characterization, multidisciplinary planning, and sustained surveillance in high-risk paratesticular rhabdomyosarcoma.