Osteoid Osteomas and Osteoblastomas are both benign primary bone tumors.
Osteoid osteomas are slow growing bone tumors that typically present in patients under 25 years old. The exact pathophysiologic mechanism for this disease remains unknown. However, bones undergo rapid growth between the age of 4 to 25. As such, both osteoclastic and osteoblastic activity is increased during these years which can contribute to the development of pathophysiologic changes.
The most common location for osteoid osteomas is the cortex of long bones. The most commonly involved bones are the femur, tibia, and humerus.
The pain associated with Osteoid osteomas is relieved by NSAIDs. Typically, a well vascularized zone in the middle of the tumor, called a nidus, is present. High levels of cyclooxygenase-2 expression, prostaglandin E2 and prostacyclin are found in the proximity of the nidus. These mediators promote neovascularization of the nidus.
In patients with osteoid osteomas, pain is typically increased at night. This pain can be dull, achy, or so severe as to wake up patients from sleep.
Osteoid osteomas are slow-growing tumors that rarely grow above 2 cm in diameter.
The surrounding sclerosis is due to inflammatory changes that damage adjacent bone tissue. Attempted cellular repair of this tissue yields altered bone structure and composition. Subsequently, high levels of collagen and reticulin can be seen in the sclerotic area.
Osteoblastomas, like osteoid osteomas, are benign slow growing primary bone tumors. They are typically encountered in patients between the ages of 10 - 20 years old.
In contrast to osteoid osteomas, osteoblastomas typically involve the vertebrae. In select cases, the tumor can grow and exert compression on the spinal cord. This can lead to neurological symptoms.
In contrast to osteoid osteomas, the pain associated with osteoblastomas is not relieved by NSAIDs. In contrast to osteoid osteomas, the pain which occurs in osteoblastomas does not have a nocturnal predominance. Instead, the pain is chronic and localized to the area of the tumor.
Osteoblastomas typically grow to be more than 2 cm in diameter.
Osteoblastomas present as radiolucent lesions without surrounding sclerosis on bone X-ray. This is in contrast to Osteoid Osteomas which present with surrounding sclerosis.
Surgery is preferentially used to treat osteoblastomas given their larger size. The preferred treatment option is curettage with bone grafting. However, surgery can also be used sparingly in osteoid osteomas in cases in which the pain is not responsive to medical treatment.
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