Bizarre parosteal osteochondromatous proliferation: Rare case affecting distal ulna and review of literature.

Bizarre parosteal osteochondromatous proliferation (BPOP) or Nora's lesion, is a rare benign surface-based bone lesion most commonly involving the tubular bones of hands and feet. We report an unusual case of BPOP affecting the distal ulna in a 22-year-old man who presented with a painless wrist mass following injury and was successfully treated with surgical resection. We focus on multi-modality imaging, histopathology, and differential diagnosis (including osteochondroma, florid reactive periostitis, myositis ossificans, and surface-type osteosarcoma), as well as a review of the literature regarding recent concepts on etiology and evolution, spectrum of imaging characteristics and diagnostic overlap, histopathology, as well as treatment options.