Bizarre parosteal osteochondromatous proliferation (Nora's lesion). Description of six cases and a review of the literature.

The authors report their experience with 6 cases of bizarre parosteal osteochondromatous proliferation (BPOP) observed in 4 patients in its typical site (distal ends of the limbs), and in 2 patients where it was instead atypically localized in the humerus and femur. The histories of the patients revealed that 50% reported previous trauma in the site of lesion. Five patients were submitted to surgical exeresis, while the remaining patient refused to undergo any type of treatment because he was asymptomatic. At a mean follow-up of 36 months 1 patient presented with recurrence (20%). BPOP is a rare pseudotumorous lesion with typical radiographic and histopathologic findings similar to to those of other benign and malignant tumor forms. A review of the small amount of literature in existence is used to analyze the elements that may lead to accurate differential diagnosis.