Author(s)

Tadahiko Utsunomiya^1*, Masaaki Suemitsu¹, Miyuki Morikawa¹, Masanobu Matsuno², Hirotsugu Yamamoto¹, Hitomi Sakata¹, Kazuhiro Hasegawa¹, Masahiro Higuchi¹, Kayo Kuyama¹

¹Department of Oral Pathology, Nihon University School of Dentistry at Matsudo, Matsudo, Japan.
²Department of Anatomy, Nihon University School of Dentistry at Matsudo, Matsudo, Japan.

Myositis ossificans (MO) is an extraskeletal tumor-like lesion with bone formation, and is relatively rare in the head and neck region. We report herein a clinicopathological analysis of MO associated with a muscle of mastication. The patient was a 70-year-old Japanese woman who presented with a tumorous mass in the right parotid area and no history of trauma. The surgically excised tumorous lesion consisted of proliferating fibroblastic cells with no atypia in the central portion, and a formation of trabecular osteoid and/or bony tissue in the peripheral portion as the so-called “zonal phenomenon”. The final histological diagnosis was MO, and the lesion was located in the posterior belly of the digastric muscle on computer tomography. A review of the literature showed that many cases of MO predominantly affected the medial pterygoid and masseter muscle and showed a history of previous trauma. The present case represents a rare case of nontraumatic MO in the uncommon location of the posterior belly of the digastric muscle.

Myositis Ossificans, Muscle of Mastication, Heterotopic Ossification, Histopathology

Utsunomiya, T. , Suemitsu, M. , Morikawa, M. , Matsuno, M. , Yamamoto, H. , Sakata, H. , Hasegawa, K. , Higuchi, M. and Kuyama, K. (2016) Nontraumatic Myositis Ossificans in a Muscle of Mastication. Open Journal of Stomatology, 6, 135-139. doi: 10.4236/ojst.2016.65017.