Bone: Osteoid Osteoma

Note Osteoid osteoma (OO) is defined as a benign boneforming tumour characterized by small size, limited growth potential and disproportionate pain (WHO, 2002). Usually, OO is solitary, although the literature shows few reports of multiples lesions in the same patient, but not concomitant. In most cases, OO patients complain of severe nocturnal pain that usually responds to salicylates and nonsteroidal anti-inflammatory drugs (NSAIDs). The exact mechanism of the pain in OO and why it is more intense at night is still unknown. Some reports have shown that the nidus is responsible for the severe pain, as evidenced by the disappearance of pain when the nidus is completely excised, and that prostaglandins seem to play a major role. Prostaglandin E2 is believed to prompt vasodilation and pain. An increase concentration of prostaglandin has been found in the nidus of the lesion, as well as, a strong positivity for cyclooxy-genase-2 (a key enzyme in the production of prostaglandins, particularly prostaglandin E2).