Myositis Ossificans Mimicking Soft Tissue Neoplasm

Abstract

Myositis ossificans is a benign condition of heterotopic bone formation. It is a relatively uncommon disease, and differential diagnosis can be difficult because many findings are typical but not pathognomic. We report a patient with early myositis ossificans traumatica, which was not diagnosed until a surgical specimen was obtained. This 65-year-old man presented with a swollen painful lump over his left anterior arm after a session of Kung Fu training. Imaging findings were equivocal and a neoplastic process could be excluded. Exploratory surgery was performed to ascertain the nature of the lesion and pathology revealed pathognomonic features of myositis ossificans. The lump resolved with medical treatment several weeks later. Prompt diagnosis of atypical or early myositis ossificans requires that radiologists maintain a high index of suspicion when a patient presents with a post-traumatic lump, even when radiographic findings are equivocal or negative. A watchful-waiting approach with serial plain radiography and ultrasonography may avoid unnecessary surgical procedures in these cases.