Myositis Ossificans - Morphology

Myositis Ossificans (MO) - Peripheral Zone: In the outermost layer (periphery of the lesion), the osteoid of immature woven bone undergoes mineralization to form parallel arrays of lamellar bone with round osteocytes. A sampling from this area may be mistaken for an osteoma, if taken out of context. Long standing MO lesions may also develop fatty or hematopoietic marrow in the peripheral zone.