Abstract
Background: Bizarre parosteal osteochondromatous proliferation [Nora’s lesion] is a rare tumourous lesion with aggressive growth that affects primarily the small tubular bones of extremities and often recurs after excision. It is often confused with chondrosarcomas, parosteal osteosarcomas and florid reactive periostitis.
Materials and Methods: The clinical and pathological findings in eight cases of Nora’s lesion from the Scottish bone tumour registry are presented.
Results: There were eight lesions reported in the registry. (5 female & 3 male). Anatomically there was 1 metacarpal lesion, 2 proximal phalanx lesions, 3 middle phalanx lesions and 2 distal phalanx lesions. Age at presentation ranged from 25 – 65 years (mean 41y). The common mode of presentation was pain and swelling for a period of 6 months to 2 years. There was no history of trauma. Two patients were initially misdiagnosed, one as synovial chondromatosis and the other as an osteochondroma. Treatment was in the form of an excision biopsy. The recurrence rate after excision was 62.5%. 60 % of recurrences occurred within 12 mts of excision. One phalangeal lesion recurred twice after excision. There was no distal metastasis.
Discussion: Bizarre parosteal osteochondromatous proliferation is histologically composed of bony, chondroid and fibrous proliferation, with a high cellular density and bizarre chondrocytes but is devoid of cellular atypia or necrosis. It is a rare pseudotumorous lesion, with typical clinical, radiographic and histopathology findings similar to those of other benign and malignant tumours. The rarity of this lesion and the high local recurrence rate necessitate an accurate histological diagnosis and complete excision.
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