Giant nontraumatic myositis ossificans in a child: A case report

Figure 1 Appearance photo of right thigh. A large mass at the posterior of the right thigh with redness and swelling.

Figure 2 Radiographic images of the right thigh over time. A: Lateral view radiograph at the 2^nd week, soft tissue in the posterior of the right upper femur was swollen, and there was faint calcification; B: Lateral view radiograph at the 7^th week. A large mass of calcification appeared at the original location; C: Lateral view radiograph at 9^th months, the mass of calcification is denser than before.

Figure 3 Computed tomography of the right thigh over time. A: Sagittal view of Computed tomography (CT) at 2^nd week. Mass can be seen in the muscle tissue of the posterior upper right thigh, which has a slightly low density and irregular flaky calcification; B: Sagittal view of CT at 7^th week. The mass is larger than before, and calcification is like an eggshell with peripheral calcified rim and low density in the central zone compared to muscle; C: Sagittal view of CT at the 9^th month. This calcification is denser than before. CT: Computed tomography.

Figure 4 Intraoperative surgical pictures and gross appearance and microscopic pictures of the tumor. A: The mass is located between muscle spaces and has a complete capsule; B: Specimens of gross appearance, gray–red hard mass, size approximately 14.0 cm × 8.7 cm × 8.2 cm. C: (40 ×) The tumor shows zoning, fibroblast/myofibroblast hyperplasia in the center, inflammatory cell infiltration, and multinucleated giant cell formation, and the surrounding bone trabeculae are arranged in a mesh, and the surrounding osteoblasts are attached.