Malignant Mesothelioma of the Tunica Vaginalis in a Pediatric Patient: A Case Report of a Rare Tumor with Medicolegal Implications

INTRODUCTION: Although exceedingly rare in children, malignant mesothelioma of the tunica vaginalis may be misinterpreted as more common pediatric testicular neoplasms due to overlapping histological features reported in isolated cases. Diagnostic errors can cause delayed treatment and legal consequences. CASE PRESENTATION: A 15-year-old male presented in Turkiye with abdominal distension, scrotal swelling, and suspected testicular malignancy. Pathology suggested a Leydig cell tumor, and chemotherapy was initiated. His condition deteriorated, leading to reevaluation abroad. Pathological reassessment from three international centers, including a German laboratory, confirmed malignant mesothelioma of the tunica vaginalis. The patient improved with appropriate treatment. Due to diagnostic discrepancies, a malpractice case was initiated in Turkiye. CONCLUSION: This case highlights the importance of accurate histopathological diagnosis in pediatric testicular tumors. Given the rarity of tunica vaginalis mesothelioma, multidisciplinary collaboration and second-opinion pathology reviews are essential for proper management and medicolegal accountability.