Abstract
Myositis ossificans (MO) is a rare, benign ossifying lesion characterized by focal formation of heterotopic bone and cartilage in extraskeletal soft-tissue that most commonly occurs in young adults. In most cases, no causative factor can be identified. The diagnosis of MO is usually based on the patient's history of trauma, clinical signs, on imaging appearance and histological examination. We present a non-traumatic MO case of the forearm in a 40-year-old man with weakness in left finger motion, a decrease in prehension for more than three weeks, without any weight loss, malaise, anorexia or fever. The clinical symptoms and radiological findings can be easily confused with malignant lesions. Treatment is usually conservative but, due to the limited strength and range of motion of the left hand, the tumor was extirpated and the diagnosis of MO was made by biopsy. The patient had no neurological deficits after surgical treatment and was discharged on the fifth day after the surgery in good condition with the recommendation to begin a rehabilitation program.