Solid Aneurysmal Bone Cyst in the Rib: A Case Report with Review of Literature

Abstract Solid aneurysmal bone cysts (ABCs) are rare tumors first identified by Sanerkin et al in 1983. While they commonly occur in long bones and the vertebral column, their presence in the ribs is unusual and poses distinct diagnostic and treatment challenges. This report discusses a case of a giant solid ABC in an 11-year-old girl who presented with a mass on the left side of her chest. A CT scan revealed a large expansile lytic lesion on the left third rib, measuring 18 × 17 × 13.5 cm, initially raising suspicion of Ewing sarcoma. A tru-cut biopsy identified a spindle cell neoplasm with multinucleated giant cells, indicative of an ABC, though giant cell-rich osteosarcoma needed to be ruled out. The patient underwent rib resection, and histopathological analysis revealed a neoplasm with solid fibroblastic areas and blood-filled cystic spaces separated by fibrous septa, along with scattered osteoclast-type giant cells. This case represents the largest solid ABC reported to date and underscores the crucial role of histopathology in diagnosing small biopsy samples.