Myositis ossificans in the infraspinatus muscle: The key to diagnosis

Abstract

The zone phenomenon is the most important diagnostic feature in differentiating myositis ossificans from malignancies such as osteosarcomas, which calcify from the center to the periphery and its presence in our late‐stage lesion was the key to diagnosis.

Aggressive atraumatic myositis ossificans in a toddler

“…MRI images can add to the confusion if obtained too early in the development of the MO. Under MRI studies MO presents as a heterogeneous mass iso or hyperintense in T1 and hyperintense in T2-weighted sequences with surrounding edema [10 , 12] . On contrasted enhanced sequences a hyperintense rim, also called “zone phenomenon,” can be observed, however, heterogeneous gadolinium enhancement is not infrequent, likewise advising caution as to being differentiated from soft tissue sarcomas [13 , 23] .…”

“…MO undergoes 3 different stages, initial development (<4weeks), mid-stage (4-8 weeks) and finally mature stage (>8 weeks); features noted on imaging studies as well as histologic examination correlate with the distinctive phases [9] , [10] , [11] . On radiographic images, in the early phase a flocculent opacity with no ossification is initially noted, however, during the subsequent phase a peripheral ossification rim develops until it reaches its mature image of “eggshell calcification” in the final stage [10 , 12] . When present in tendons or ligaments, the shape of the MO follows that of the involved structure [12] .…”

Myositis ossificans mimicking sarcoma: a not so rare bioptic diagnostic pitfall

“…The typical peripheral calcifications are detectable between the fourth and tenth week when the lesion stops growing. Once the lesion is mature, the so-called “zonal pattern organization” can be radiologically and histologically appreciated, consisting on a central area of proliferating fibroblasts with possible necrosis and haemorrhage, followed by an intermediate zone of immature osteoid tissue along with cartilage, resulting from enchondral ossification and an outer shell of lamellar mature bone [ 6 , 7 ].…”