Role of MRI in the differentiation of early myositis ossificans and soft-tissue sarcoma

Myositis ossificans (MO) is a benign, self-limiting condition characterized by abnormal ossification of soft tissue. MO occurs most commonly in the setting of trauma, however can also develop spontaneously. A peripheral rim of zonal calcification within the affected region represents the classic late-stage appearance and is considered virtually pathognomonic. During the early stages of MO development, diagnostic uncertainty may, however, arise as its imaging features can demonstrate overlap with malignant lesions such as soft-tissue sarcoma. This may lead to unnecessary further investigations, including image-guided biopsy. Recognition of the imaging features of early MO using magnetic resonance imaging (MRI) can provide the radiologist with more diagnostic certainty and help obviate the need for unnecessary investigation of this benign entity. This case offers an example of how MRI can achieve this diagnosis during the early multimodality investigation of an indeterminate soft-tissue mass.