Retroperitoneal Teratoma in a Newborn: A Case Report and Diagnostic Insights.

Retroperitoneal teratomas are rare neoplasms in neonates, presenting with nonspecific symptoms and variable clinical features, making diagnosis challenging. Radiological investigations, particularly fetal ultrasound and contrast-enhanced computed tomography, play a critical role in their detection. Differential diagnoses include neuroblastoma, adrenal hemorrhage, and congenital cystic lesions, which share overlapping clinical and imaging features. This case report describes a neonate delivered at 39 weeks of gestation, weighing 2.93 kg, to a 30-year-old gravida 2, para 1 mother with unremarkable serological tests during pregnancy. Fetal ultrasonography performed at 31 weeks, followed by magnetic resonance imaging at 35 weeks, revealed a large, multi-cystic, and solid lesion located above the left kidney. Postnatal physical examination identified a firm, non-tender abdominal mass that was confined to the left side and did not cross the midline. Imaging studies, including abdominal radiographs, ultrasonography, and contrast-enhanced computed tomography, confirmed a large left supra-renal mass. Meta-iodo-benzyl-guanidine scintigraphy combined with single-photon emission computed tomography showed no activity in the mass. Serum alpha-fetoprotein levels were within the normal range for term neonates, and the infant had normal beta-human chorionic gonadotropin and urine homovanillic acid levels. The infant underwent exploratory laparotomy on the sixth postnatal day, confirming an immature teratoma without malignant components. Postoperatively, AFP levels demonstrated the expected physiological decline, consistent with the absence of malignant components. The infant was discharged on postnatal day 35. This case highlights the diagnostic complexities of retroperitoneal teratomas in neonates and underscores the critical role of antenatal ultrasound and a multidisciplinary approach in ensuring effective diagnosis and management.