Pseudomalignant Myositis Ossificans of the Neck in a Child: Case Report and Review of the Literature.

Abstract

Myositis ossificans is a benign process of heterotopic bone formation developing in soft tissues that can mimic malignancy. Differential diagnosis can be difficult without a biopsy when it originates in atypical locations. A 5½-year-old boy was admitted for a cervical tumor causing torticollis. The nodular tumor developed at the lateral border of the right C3-4 foramen, had calcification/ossification at its periphery, and was accompanied by a huge edematous reaction of the scalene muscles. The patient underwent an extensive work-up by pediatric oncologists. A biopsy was requested because of high suspicion of malignancy. At surgery, the lesion was benign on frozen sections and was completely resected, allowing the diagnosis of myositis ossificans. The patient made a rapid and complete recovery. Myositis ossificans circumscripta is rare in children, especially in the neck region. The diagnostic challenge is to differentiate it from bone and soft tissue malignancies. Appropriate management, including surgery if needed, leads to an excellent outcome. Another concern is to exclude fibrodysplasia ossificans progressiva when atraumatic myositis ossificans develops in a young child in the neck or shoulder region.