Bizarre parosteal osteochondromatous proliferation or Nora’s lesion affecting the extremities: A concise update

Abstract

The bizarre parosteal osteochondromatous proliferation or Nora’s lesion is an unusual clinical entity that presents with localized swelling and pain. The characteristic radiological appearance includes a cluster of variably calcified lesions adjacent to a particular bone. However, it does not necessarily have direct continuity with its medullary region. The etiopathogenesis of this disorder is not yet fully understood. Various other lesions require careful exclusion and the use of advanced imaging modalities to supplement the diagnosis. The final diagnosis of the lesion, however, is based on the histopathological basis. However, these lesions are reported as sporadic reports or small series in the literature and are also discovered in areas other than the common locations in hands and feet. The recent research aims to throw more advanced knowledge into their causation, including genetic etiology. The symptomatic lesions may require excision for clinical relief, but recurrence is not uncommon. The future research, and preferably multi-center collaboration, is required for more insight into their comprehensive nature and clinical spectrum. A brief and crisp update of the articles published in the past 10 years describing bizarre parosteal oseochondromatous proliferation in the extremities is presented here for educational purposes for orthopedists and generalists alike.

Bizarre Parosteal Osteochondromatous Proliferation (Nora Lesion) Mimicking Giant Cell Tumour of Tendon Sheath: A Case Report

“…Such features have also been reported in the literature for cases of giant cell tumour of tendon sheath [7]. Typical radiographical features of Nora lesion described in the literature include cortical bony growth projecting into the soft tissue while lacking connection with medullary cavity [2]. A lack of medullary involvement helps characterize BPOP from osteochondroma, its main differential.…”

“…Nora lesion is notorious for having a high tendency to recur, with recurrence rates between 29% and 55% reported within 2 years after excision [1,2]. We proceeded with excision of the mass with the capsule and periosteal tissue beneath, followed by decortication of the underlying cortical bone via a small rongeur.…”

“…It often affects the small bones of the hands and feet, presenting as a parosteal mass. Although a benign entity, high recurrence rates close to 50% following surgical excision have been reported [2]. Since the time of its discovery, few cases have been reported as sporadic case reports or small series in the literature.…”