Myositis ossificans in a child: report of a case and review of literature

ZHANG Nan; HE Le-jian

doi:10.3969/j.issn.1007-8096.2017.08.005

Abstract：Objective To study the clinicopathological features of myositis ossificans of children and to explore its histogenesis,diagnosis and differential diagnosis.Methods A case of myositis ossificans was analyzed with pathological morphology and immunohistochemical staining and review of the related literatures.Results A male patient of 12 years old was admitted to the hospital because of left hip pain after local trauma for 1 month.On radiologic examination,at the end of 1 st,2nd and 4th week,the results of plain radiograph were different;the first two times,no obvious mass was found;the last time examination showed one mass in front of left hip,with lower density inside and higher density outside.Then the MRI found a mass in the skeletal muscles,without association between the mass and adjacent bone.Surgical removal was done.By pathological examination,the 3-zone pattern was found,including proliferating fibroblasts,immature bone with amount of osteoblasts and mature bone from inside to outside.The fibroblasts coexpressed SMA and CD68,and about 25％ cells expressed Ki-67.Conclusion Myositis ossificans is a rare lesion in children.It has characteristics in clinic,radiology and pathology.It is a benign neoplastic lesion in soft tissue,especially skeletal muscles,with favorable outcome.