What are enostosis spinal tumors?

Updated: Nov 01, 2018
  • Author: Andrew A Sama, MD; Chief Editor: Jeffrey A Goldstein, MD  more...
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Also termed a bone island, enostosis is a mass of calcified medullary defects of lamellar compact bone with haversian systems found within the cancellous portion of the bone. It occurs most frequently in the thoracic and lumbar spine, usually between T1 and T7 and between L1 and L2. Enostosis is one of the most common lesions to involve the spine.

Enostoses are usually stage 1 lesions and are discovered incidentally. Most remain stable, but some may slowly increase in size. Resnik et al determined the incidence of enostosis to be approximately 14% in cadavers. [13]

Radiographically, enostoses are circular or oblong osteoblastic lesions with a spiculated margin, which gives it the appearance of thorny periphery. An abrupt transition from normal to the sclerotic bone is exhibited on the radiograph. Bone scan findings are usually normal, and magnetic resonance imaging (MRI) demonstrates low signal intensity with normal surrounding intensity.

Enostosis sometimes can be confused with osteoblastic metastatic disease. Enostosis can be differentiated by lack of activity on bone scan, by the normal appearance of adjacent bone, by its thorny margins, and by lack of a primary tumor for metastasis. If the enostosis exhibits an increase in diameter of greater than 25% in 6 months, a biopsy should be performed.

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