Myositis Ossificans - Introduction
Image Description
Introduction: Myositis ossificans (MO) is a benign, solitary, self-limited, ossifying mass that is usually found within the musculature of the extremities. The term is a misnomer on several counts. It can occur in non-muscle tissues, there is little or no inflammation and the initial stages show no bone formation. It is related to fibro-osseous pseudotumor of digits and soft tissue aneurysmal bone cyst.
The lesion passes through three parallel stages of clinical, radiologic and histopathologic changes. The initial stage (first 4 weeks) is highly cellular and can mimic a sarcoma (right half of the image). The intermediate stage (4-8 weeks) is characterized by the appearance of osteoblastic matrix and immature woven bone (center of the image). The mature stage (> 8 weeks) shows abundant mature lamellar bone and can mimic osteoma (left one-third of the image). The lesion becomes smaller as it matures and may eventually regress.
The lesion passes through three parallel stages of clinical, radiologic and histopathologic changes. The initial stage (first 4 weeks) is highly cellular and can mimic a sarcoma (right half of the image). The intermediate stage (4-8 weeks) is characterized by the appearance of osteoblastic matrix and immature woven bone (center of the image). The mature stage (> 8 weeks) shows abundant mature lamellar bone and can mimic osteoma (left one-third of the image). The lesion becomes smaller as it matures and may eventually regress.