Sonographic diagnosis Calcification is typically depicted 2 weeks earlier by ultrasound (US) when compared to radiographs. The lesion develops in two distinct stages with different presentations at US. In the early stage, termed immature, it depicts a non-specific soft tissue mass that ranges from a hypoechoic area with an outer sheet-like hyperechoic peripheral rim to a highly echogenic area with variable shadowing. In the late stage, termed mature,<unk>  is depicted as an elongated calcific deposit that is aligned with the long-axis of the muscle, exhibits acoustic shadowing, and has no soft tissue mass associated. US may suggest the diagnosis at early stage, but imaging features need to evolve with successive maturation of the lesion and formation of the characteristic late stage changes before they become pathognomonic. The differential diagnosis includes many tumoral and nontumoral pathologies. A main concern is to differentiate early<unk>  from malignant soft-tissue tumors, and the latter is suggested by a fast-growing process. If clinical or sonographic findings are dubious and extraosseous sarcoma is suspected, biopsy should be performed. At histology, detection of the typical zonal phenomenon is diagnostic of<unk> , though microscopic findings may be misleading during the early stage. Radiologic diagnosis The radiological features of<unk>  are ‘faint soft tissue calcification within 2–6 weeks, (may have well-defined bony margins by 8 weeks) separated from periosteum by lucent zone and on CT, the characteristic feature is peripheral ossification’.
Myositis ossificans
Osteoma cutis
Fibrodysplasia ossificans progressiva
Leri pleonosteosis
Osteitis fibrosa cystica
Osteochondritis dissecans
Enchondromatosis
Osteofibrous dysplasia