Neonatal Intra-abdominal Mixed Germ Cell Tumour with Retroperitoneal Extension Mimicking Hepatoblastoma—A Diagnostic Challenge: A Case Report

Background: Neonatal germ cell tumours (GCTs) are rare, and intra-abdominal mixed GCTs are even less common. Although most solid tumours in neonates are benign, malignant cases occur at an estimated rate of 1 in 27,500 live births, accounting for about 2% of all childhood cancers. Differentiating benign from malignant neonatal neoplasms is a significant diagnostic challenge due to overlapping clinical and radiological features. We report one of the few documented cases of an intra-abdominal mixed GCT in an Indian neonate, highlighting the importance of early recognition and a multidisciplinary management approach. Case Presentation: A 2-month-old male infant presented with progressive abdominal distension and constipation since the 15th day of life. Abdominal examination revealed a firm, non-mobile, irregular mass measuring 10 × 8 cm in the upper abdomen. Imaging studies identified a large intra-abdominal mass with retroperitoneal extension initially suspected to represent hepatoblastoma. Intraoperative findings revealed a 12 × 10 cm tumour adherent to the left lobe of the liver and extending into the retroperitoneum. Histopathological examination confirmed a malignant mixed GCT comprising yolk sac and teratomatous elements. The patient underwent left lateral segmentectomy followed by adjuvant bleomycin, carboplatin, and etoposide (BEP) chemotherapy. He remains disease-free at 3-year follow-up, with normalised serum alpha-fetoprotein (AFP) levels and no evidence of recurrence on magnetic resonance imaging (MRI). Conclusion: This case illustrates the diagnostic complexity and surgical challenges inherent to neonatal intra-abdominal mixed GCTs with retroperitoneal extensions. The atypical location and initial radiological misdiagnosis highlight the necessity of comprehensive tumour marker evaluation, advanced imaging, and multidisciplinary collaboration for accurate diagnosis and optimal management. Early recognition, multidisciplinary evaluation, and timely intervention facilitated successful management in the present case. However, longer follow-up and additional reports are required to characterise outcomes in this rare neonatal tumour better. Keywords: acute abdomen, mixed germ cell tumor, retroperitoneum, case report