Diagnosis 10min The classic radiographic appearance is that of a centrally located,oval or round surrounded by a zone of uniform bone sclerosis;this combination is virtually diagnostic of osteoid osteoma Bone cyst Bone cyst is a usually cavitary lesion of bone. Causes 10min Bone cysts may occur after trauma and in osteoarthritis.rheumatoid arthritis. neurofbromatosis and calcium pyrophosphate dihydrate crystal deposition disease. Pathological Types 10min Simple bone cysts:These cysts occur most frequently in long tubular bones especially the metaphysis,and in the bony pelvis. Radiographically.these lesions appear radiolucent and are located centrally. with cortical thinning and mild expansion of the bone Aneurysmal bone cysts:They occur most frequently in the spine and long tubular bones,particularly the metaphysis.and in most cases result from trauma Radiographically the lesions tend to be eccentric and occasionally trabeculated Epidermoid cysts:They occur almost exclusively in the terminal phalanges an skull.These cysts are well-defined osteolytic lesions with sclerotic margins and frequently soft tissue swelling. Intraosseous ganglion cysts:They occur predominantly in subchondral regions of tubular bones.carpal bones,and acetabulum.These osteolytic lesions are usually solitary.are sharply circumscribed,and vary in size Outlines, requirements and time allocation Diagnosis ⚫ The classic radiographic appearance is that of a centrally located, oval or round radiolucent area ⚫ surrounded by a zone of uniform bone sclerosis; this combination is virtually diagnostic of osteoid osteoma Bone cyst Bone cyst is a usually cavitary lesion of bone. Causes ⚫ Bone cysts may occur after trauma and in osteoarthritis, rheumatoid arthritis, neurofibromatosis and calcium pyrophosphate dihydrate crystal deposition disease. Pathological Types ⚫ Simple bone cysts: These cysts occur most frequently in long tubular bones, especially the metaphysis, and in the bony pelvis. ⚫ Radiographically, these lesions appear radiolucent and are located centrally, with cortical thinning and mild expansion of the bone ⚫ Aneurysmal bone cysts:They occur most frequently in the spine and long tubular bones, particularly the metaphysis, and in most cases result from trauma. ⚫ Radiographically the lesions tend to be eccentric and occasionally trabeculated ⚫ Epidermoid cysts: They occur almost exclusively in the terminal phalanges and skull. These cysts are well-defined osteolytic lesions with sclerotic margins and frequently soft tissue swelling. ⚫ Intraosseous ganglion cysts: They occur predominantly in subchondral regions of tubular bones, carpal bones, and acetabulum. These osteolytic lesions are usually solitary, are sharply circumscribed, and vary in size 10min 10min 10min