Purpose or Case Report: A 3-year-old boy presented with fever, cough, and breathlessness for 7 days. He had a prior history of recurrent respiratory distress episodes requiring mechanical ventilation. On examination, he was tachypneic with left-sided decreased chest expansion, tracheal deviation to the right, and impaired percussion notes. Chest radiograph revealed a large left thoracic opacity with mediastinal shift. Contrast-enhanced CT showed a large, well-defined anterior mediastinal mass (approximately 12 × 8 × 5 cm) with predominantly soft-tissue attenuation and focal fat densities, suggesting thymolipoma or thymolymphoma.
USG-guided core biopsy initially revealed scant thymic tissue with Hassall corpuscles, favoring thymic origin but non-diagnostic. A repeat CT-guided biopsy showed a biphasic pattern of thymic epithelial cells admixed with lymphocytes. The child underwent complete surgical excision of the mass via an extrapleural approach. Grossly, two encapsulated masses (19 × 13 × 4.5 cm and 9 × 6.5 × 4 cm) were noted with smooth surfaces and lobulated gray-white cut surfaces. Histopathology confirmed WHO Type A thymoma, with intact capsule margins.
Methods & Materials:
Results: This case highlights a rare instance where a thymoma radiologically mimicked a thymolipoma due to the presence of fatty components. While thymolipomas are benign lesions curable by excision, thymomas carry malignant potential and require long-term follow-up. Radiologic–pathologic correlation is essential, as imaging findings alone may be misleading.
Conclusions: A fatty anterior mediastinal mass in a child, though suggestive of thymolipoma, can rarely represent thymoma. Repeat biopsy and histopathologic confirmation are crucial when imaging and initial biopsy findings are inconclusive.