Background: Myositis ossificans and ossifying fibromyxoid tumor are rare entities. They share a lot of similarities as far as localization, clinical and radiological picture and outcome are concerned.
Case report: The authors describe a case of a 15-year-old boy who was operated on for ossifying tumor localized in the right lumbar region. Preoperative X-ray and CT revealed the tumor with clear borders of round shape and multiple calcifications, particularly towards the periphery. The boy made an uneventful postoperative progress. The histopathology of the tumor was as follows: multiple mature osseous trabeculae dispersed in richly vascularized matrix, the presence of multiple fibroblasts and some polynuclear cells. Immunohistochemistry showed NSE (neuron specific enolase)–positive and weakly vimentin-positive reactions. The results may suggest neural origin of the tumor. The differential diagnosis of both entities: myositis ossificans and ossifying fibromyxoid tumor is discussed.
In spite of immunohistochemistry, supporting the option of fibromyxoid tumor diagnosis, the specificity of these results is controversial and so the possibility of myositis ossificans can not be excluded.
Conclusions: In summary, the authors share the opinion suggesting the probability, at least in some cases, of common roots of the above mentioned diseases.

Keywords: Myositis Ossificans, ossifying fibromyxoid tumor