Cystic bone Lesions: Diagnostic pitfalls and therapeutic considerations

Bone tumors are rare lesions that often pose diagnostic and therapeutic challenges for an orthopedic surgeon. Malignant bone lesions comprise <0.2 % of all cancers and the precise incidence of benign bone lesions is not documented. Many of these lesions appear cystic on imaging with varying number of overlapping features between benign lesions like Unicameral bone cyst, locally aggressive like Aneurysmal bone cyst, infections like hydatid cyst of bone to malignant like telangiectatic osteosarcoma. To aid the diagnosis, cystic bone lesions are classified into primary and secondary bone cysts. Primary bone cysts include simple bone cysts (SBC), aneurysmal bone cysts (ABC), epidermal inclusion cysts, intraosseous ganglion, intraosseous lipoma, and hydatid cysts of bone. Secondary bone cysts arise within a primary bone condition leading to cyst formation and include pathologies like fibrous dysplasia (FD), telangiectatic osteosarcoma, eosinophilic granuloma, Giant cell tumor (GCT) of bone and brown tumors. Each of these has peculiar diagnostic hallmarks, requires different treatment, and carries different prognosis. Due to their rarity and overlapping clinico-radiological features, cystic lesions often pose diagnostic and therapeutic dilemmas for clinicians and radiologists, often leading to errors in diagnosis and inadequate treatment which can endanger a patient's limb or life. Through this article, we aim to describe specific diagnostic hallmarks and treatment plans for these cystic bone lesions which can aid radiologists and treating orthopedic surgeons in diagnosing and manage these lesions optimally.