Progressive abdominal distension as an unusual presentation of mediastinal teratoma in an infant: A case report and literature review

Mediastinal masses in pediatric patients often pose a significant diagnostic challenge for both clinicians and radiologists due to their broad spectrum of etiologies, ranging from benign lesions to malignant conditions. 
Mediastinal teratomas are germ cell tumors that typically arise in the anterior mediastinum and, less commonly, in the posterior mediastinum. They represent the most frequent form of extragonadal germ cell tumors [1].
We report the case of a 02-year-old female infant with no significant past medical history, who presented with progressive, asymmetric abdominal distension predominantly on the left side, noted over one year by her mother, with preserved general condition.
On physical examination, the patient was in good general condition and afebrile. Abdominal examination revealed a firm left subcostal mass fixed to deep planes, associated with clinical signs suggestive of a left basal pleural effusion.
Chest radiography followed by thoraco-abdominal CT scan revealed a large posterior mediastinal mass occupying nearly the entire left hemithorax. The lesion was mixed solid-cystic, containing fat and scattered calcifications, and caused a significant mass effect with contralateral mediastinal shift and diaphragmatic depression.
Biological investigations showed elevated alpha-fetoprotein (AFP) and negative β-hCG. Initial biopsy suggested a mature teratoma without immature components in the sampled tissue. The patient underwent neoadjuvant chemotherapy followed by complete surgical excision of the mass.
Histopathological examination of the surgical specimen confirmed an immature pluritissular teratoma, grade 1.
The postoperative course was uneventful, with favorable clinico-radiological evolution. The patient is currently under regular follow-up.