The nidus in osteoid osteoma may sometimes undergo extensive mineralization resulting in confluent areas of osteoid and broad bony trabeculae. The appearance may mimic Paget's disease of bone. Previously, the standard treatment of osteoid osteomas was surgical excision of the nidus - a procedure that is rarely done now. Most patients now undergo thermal ablation under CT guidance. Patients note the relief of pain in the immediate post-surgery period. Prognosis is good. There are no reports of malignant transformation.