Giant Lipoma of the Thoracic Wall in a Two-Year-Old Girl: Imaging Features Supporting a Benign Diagnosis

Lipomas are the most common mesenchymal neoplasms of soft tissue, but giant lipomas, defined as lesions exceeding 10 cm in any dimension or weighing more than 1 kg, are rare in young children, in whom lipoblastoma is the main adipocytic differential diagnosis and liposarcoma must be excluded. We report the case of a two-year-old girl with a left dorsal thoracic wall mass that had grown progressively over 18 months. A biopsy performed elsewhere one year earlier had shown mature adipose tissue without atypia. Radiography showed a large soft-tissue density mass with rib deformity, a sixth-rib fracture, and superior displacement of the scapula. Ultrasound demonstrated a solid, hypovascular mass with echogenicity similar to subcutaneous fat. Magnetic resonance imaging showed a 12.0 × 10.2 × 9.1 cm mass that followed fat signal, with signal loss on fat-suppressed sequences, no restricted diffusion, and no significant enhancement, extending through an intercostal space into the extrapleural compartment. At surgery, the tumor adhered to the chest wall muscles and ribs and extended into the sixth intercostal space, deforming the adjacent ribs and displacing the pleura and lung without invading them. It was dissected circumferentially and resected without complications. The specimen measured 13.2 × 10.1 × 10.0 cm and weighed 456 g, and histopathology showed a lipoma with a focus of ischemic necrosis and calcification. Because immunohistochemical and molecular studies were not performed, lipoma remains a presumptive diagnosis, and a mature lipoblastoma cannot be completely excluded. There was no clinical or imaging recurrence after one year of follow-up. This case illustrates imaging features that support a benign adipocytic tumor in early childhood and the limits of imaging, which cannot replace histological confirmation.