A Case of Myositis Ossificans in the Abdominal Rectus Muscle that was Difficult to Diagnose Preoperatively

Abstract

A 76-year-old man was referred to our hospital for movement-related hypogastric pain. A 23×23×52 mm, ring-enhanced, low-density area was detected in the left side of the abdominal rectus muscle on CT scan. The mass had low signal intensity on T1/T2 and high signal intensity on diffusion-weighted images of MRI. The findings of an ultrasound-guided core needle biopsy were suggestive of spindle cell sarcoma. Tumor resection was performed. The resected tumor was histopathologically characterized by bone trabecula at the periphery, called a zonal pattern, and myositis ossificans was diagnosed. There were no clinical findings of recurrence postoperatively. Since myositis ossificans in the abdominal rectus muscle is extremely rare, this case is reported along with a review of the literature.