A 6-YEAR-OLD girl presented to her pediatrician with a tender mass of the right midthigh. She admitted to a history of minor trauma 2 weeks earlier. A physical examination revealed a large, warm, tender subcutaneous mass over the anteromedial aspect of the distal right femur. Marked asymmetry in the size of the thighs was detected, with the right midthigh measuring 30 cm in circumference and the left, 26.5 cm. The patient was febrile and had an elevated erythrocyte sedimentation rate. On the basis of the clinical examination, roentgenographic (Figure 1), and computed tomographic (Figure 2) findings, diagnoses of osteo-myelitis, osteosarcoma, and myositis ossificans were considered. The lesion was aspirated, and cultures of the aspirate were negative for bacteria. A gallium scan showed a strikingly increased uptake of radionuclide in the lesion, and surgical treatment was considered.
Denouement and Discussion
Myositis Ossificans Circumscripta
Myositis ossificans is a benign process in