MRI of myositis ossificans circumscripta.

Myositis ossificans circumscripta (or pseudomalignant osseous tumor of soft tissue) may be confused with malignant neoplasms if there is no clear history of trauma. Two cases are presented in which magnetic resonance imaging (MRI) clearly demonstrates disproportionally extensive abnormal signal intensity along the course of muscle fibers. Although the specificity of this finding is uncertain, MRI enhances the level of confidence in diagnosing myositis ossificans.