Which of the following is not true about osteoid osteoma -

Ans. is 'c' i.e., Lesion appears ill defined on x-ray with permeative margins Osteoid osteoma* Osteoid osteoma is the most common true benign tumor of the bone. This is a benign circumscribed lesion that may arise in the cortex of long bones or occasionally in the cancellous bone of spine. The characteristic feature is the formation of a small nidus of osteoid tissue, surrounded by a reactive zone of dense sclerosis (Sclerotic new bone formation).Clinical features of osteoid osteoma* The tumor occurs between 10-30 years of age and is more common in males.* The diaphysis of long bones is involved, most common bone involved is the tibia followed by femur. Posterior elements of the vertebrae may also be involved.* The presenting complaint is a nagging pain, worst at night, and is relieved by salicylates or other NSAIDs, a diagnostic feature.* On X-ray, there is a small radiolucent area (nidus) surrounded by dense sclerosis.* X-ray, in some cases, show local sclerotic thickening of the shaft that may obscure the small central nidus within the area of rarefaction.* Bone scan shows increased uptake in the nidus.* The only treatment is wide en block excision along with internal fixation with or without bone grafting.