[Circumscript myositis ossificans in a four-year-old boy]

We present the case of a 4 year old boy with no previous personal or family history of interest, who attended the Paediatric Department of our hospital after a physical examination revealed a painful induration in the left arm which had increased in size; imaging tests were consistent with a calcified mass in soft tissues, without cortical involvement, suspected of being malignant. Two-phase bone scintigraphy was requested in which a soft tissue lesion, not suggestive of malignancy, was detected. The biopsy was negative for malignant cells. However, in view of the progressive increase in size of the lesion, FDG positron emission tomography (FDG-PET) was performed, showing a hypermetabolic mass consistent with malignancy in the left arm, for which the patient underwent surgery for suspected possible parosteal osteosarcoma.