An osteoid osteoma is a benign (non-cancerous) bone tumor. It has a center of growing cells, called a nidus, surrounded by a hard shell of thickened bone. No one knows why these tumors form. They do not spread throughout the rest of the body.

Osteoid osteomas tend to be small—less than 1.5 cm in size and they may occur in any bone in the body. They are most common in long bones, such as the thigh bone (femur) and leg bone (tibia). They are also found in the hands, fingers, and spine. Osteoid osteomas may occur at any age, and are most common in patients between the ages of 4 and 25 years old. Males are affected approximately three times more commonly than females.

An osteoid osteoma causes a dull aching pain. The pain is moderately intensity, but can be severe, especially at night. The tumor is not related to previous injury, and the pain is usually not related to activity. Over-the-counter pain medicines such as aspirin, ibuprofen (Advil®, Motrin®), and naproxen (Alleve®) are helpful in easing pain. Often, people will suffer this aching, bothersome pain for years before seeing a doctor to diagnose osteoid osteoma.

The doctor will often begin diagnosing the condition by taking and evaluating X-rays of the painful bone. These tumors have a distinctive feature of thickened bone surrounding a small central core of lower density.

Such X-rays usually suggest an osteoid osteoma. Often, the doctor will use more imaging studies to exclude other possible bone problems, such as infections or malignant tumors. The physican may also order blood tests to look for signs of infection and a Computer Axial Tomography (CAT) scan to further evaluate the tumor. A CAT scan of an osteoid osteoma will commonly show the nidus—or center of the tumor.

After an osteoid osteoma is diagnosed, your doctor will discuss a treatment plan with you. These tumors have been reported to shrink on their own with no surgical intervention over several years. But the patient or family may not be willing to wait because of the associated pain.