MR imaging features of bizarre parosteal osteochondromatous proliferation of bone (Nora's lesion)

The purpose of this study was to review the imaging findings of three patients with bizarre parosteal osteochrondromatous proliferation of bone (BPOP). The plain radiographs and MRI images of three patients with BPOP were obtained and retrospectively reviewed. In two cases, BPOP involved the feet. In one case BPOP involved the hand. In all three cases, plain radiographs showed a well-defined calcium containing mass adjacent to the cortical surface of the adjacent bone. The underlying bone appeared normal in all cases. On MRI, the lesion was of low signal intensity on T1 weighted sequences in all cases. On FSE T2 weighted and STIR sequences, the lesion was of high signal in all cases. The cortex, medullary cavity and adjacent soft tissues appeared normal in all cases. While BPOP is rare and often confused with a variety of both benign and malignant lesions, there are specific radiological findings that may help to distinguish BPOP from many of its mimickers.