[Diagnostic problems of circumscribed myositis ossificans: presentation of an atypical case].

The authors report the case of a 22-year-old female suffering from thigh pain for 5 months. The first diagnosis considered was circumscribed myositis ossificans but the duration of symptoms and the radiological aspect mimicking some malignant features led to consider parosteal sarcoma as a possible diagnosis. Surgical resection was therefore requested and histological analysis confirmed the diagnosis of circumscribed myositis ossificans. This case emphasizes the difficulty in differentiating circumscribed myositis ossificans from a slowly growing tumor as both can be associated with increasing pain and a malignant radiological aspect. A surgical approach is therefore frequently necessary for definitive diagnosis and treatment.