Bizarre parosteal osteochondromatous proliferation of a phalanx

Summary A rare proliferative osteochondromatous malformation of a proximal phalanx is described. This malformation may mimic the appearance of a sessile osteochondroma or parosteal osteosarcoma on X-rays and may be mistaken for a low-grade osteosarcoma on histology, with disastrous therapeutic consequences. We found that cryotherapy followed by local excision was adequate to remove the tumour.     

Bizarre parosteal osteochondromatous proliferation (Nora's lesion): two cases

The lesion Nora described in 1983 as a bizarre parosteal osteochondromatous proliferation (BPOP) is a member of a group of osteocartilaginous surface lesions. BPOP is infrequent but new cases are regularly reported. We report two new cases with an unusual localization (ilion and distal humerus) and unusual size (9 cm for the iliac lesion). In light of these cases and reports in the literature, the main differential diagnoses of BPOP are exostosis and parosteal osteosarcoma.     

Bizarre parosteal osteochondromatous proliferation (Nora's lesion) in the hand

PURPOSE: The purpose of this study was to review our experience with a benign surface bone lesion referred to as bizarre parosteal osteochondromatous proliferation (BPOP) or Nora's lesion, named for the pathologist who described it in 1983. The lesion may be confused with a variety of tumors, particularly solitary osteochondromas, which are rare. METHODS: The files in the Department of Pathology at the Hospital for Joint Diseases were reviewed over a 21-year period for all surface bone lesions involving the tubular bones in the hand. There were a total of 10 cases of BPOP compared with only a single case of an osteochondroma. RESULTS: Radiographs generally showed a well-marginated uniformly dense mass arising from the surface of the affected bone without any disruption in its bony architecture. Surgical excision is the definitive treatment and included the fibrous pseudocapsule over the lesion, any periosteal tissue beneath the lesion, and any area of the cortex of the host bone that appeared abnormal. Although in the medical literature the recurrence rate for BPOP is high, we had only one recurrence in our series. CONCLUSIONS: BPOP is a benign surface bone lesion that may be confused with benign and malignant tumors. Although there is a cleavage plane between the lesion and host bone, we recommend excising the pseudocapsule over the lesion, any periosteal tissue beneath the lesion, and decorticating any abnormal-appearing areas in the underlying host bone. This may explain the low recurrence rate in our series.     

Bizarre parosteal osteochondromatous proliferation (Nora's lesion) of the forefoot

Nora's tumour is an uncommon benign tumour, involving mostly tubular bones of hands and feet, and characterized by a proliferation of chondroid, bony and fibrous tissues. Main differential diagnoses are osteochondroma, chondrosarcoma, and osteosarcoma. The authors report a case involving the left foot. The diagnosis was suspected by imaging characteristic features and was confirmed by histological examination. Treatment was surgical, with complete excision. There are no clinical or radiological signs of recurrence on further review one year postoperatively.     

Bizarre parosteal osteochondromatous proliferation. Difficulty in diagnosis

Nora's tumor, also known as bizarre paraosteal osteochondromatous proliferation, is an exophytic outgrowth from the cortical surface that consists of a mixture of bone, cartilage, and fibrous tissue. It is a benign lesion with atypical microscopic features and a tendency to recur. Nora reported 35 cases emerging from the bones of the hands and feet. The largest published series is of 65 cases, with 17 lesions involving the long bones. With this exception, most authors report isolated cases. Age range from 8 to 74 years but most patients are between 20 and 35 years of age, and with the lesion affecting males and females in equal proportions. Usually the presenting symptoMs are due to bony mass, with a variable growth rate (months-years), and infrequent pain. In 15-20% of the cases there was trauma in the patient history: nevertheless, Fechner and Mills report no association with trauma. Radiography shows a calcified, rounded mass emerging directly from the surface of the bone. Isotope bone scans show intense tracer uptake in the lesion. With time, the appearance progresses to the more characteristic mature bone architecture.     

Bizarre parosteal osteochondromatous proliferation (Nora's lesion) of the sesamoid: a case report

We report the a case of Nora's lesion (Bizarre Parosteal Osteochondromatous Proliferation) of the sesamoid. A 32-year-old woman presented with a painless, enlarging mass of two years duration on the plantar aspect of the first metatarsophalangeal joint of the left foot. Radiographs, Computerized Tomographs and Magnetic Resonance images, initially suggested a parosteal osteosarcoma arising from the tibial sesamoid. The mass was excised, and a histological diagnosis of Bizarre Parosteal Osteochondromatous Proliferation of bone (Nora's lesion) was made. The aggressive growth of this lesion may suggest a neoplasm clinically. Histological features, however, are those of a reactive lesion.     

Bizarre parosteal osteochondromatous proliferation (Nora's lesion). Two case reports

Bizarre parosteal osteochondromatous proliferation, or Nora's tumor, is an uncommon lesion, involving mostly tubular bones of hands and feet, arising from the cortical surface. It must be distinguishable from chondrosarcoma, parosteal osteosarcoma and florid reactive periostitis. It is a benign lesion, characterized by a proliferation of chondroid, bony and fibrous tissues. The authors report two cases involving the hand. The diagnosis can be made thanks to imaging techniques and confirmed by histological examination. The treatment is surgical, namely complete excision but there is a high rate of local relapse.     

Bizarre parosteal osteochondromatous proliferation (Nora’s lesion): report of two cases

Abstract We describe two cases of bizarre parosteal ostechondromatous proliferation (BPOP), commonly known as Nora’s lesion from the author who first described it, arising from the hands of two middle-aged patients. We emphasize the rarity of this lesion and the difficulty in diagnosis, since the histological pattern may mimic that of a malignant sarcoma.     

Bizarre parosteal osteochondromatous proliferation of the hand: report of two cases

Bizarre parosteal osteochondromatous proliferation is a rare tumor usually localized in the hand. We report two new cases, one in the thumb of a middle aged woman and one in the terminal phalanx of a young haemophiliac patient.     

Bizarre parosteal osteochondromatous proliferation of the fifth metatarsal (Nora's lesion)—Case report

We report a case of Nora's lesion (bizarre parosteal osteochondromatous proliferation) of the fifth metatarsal. A 56 year old male, presented with a painless, gradually enlarging swelling over the lateral aspect of his left foot, of 2 years in duration. Plain radiography and MRI showed features consistent with a bizarre parosteal osteochondromatous proliferation of bone (Nora's lesion). The mass was excised and the lesion confirmed histologically. This benign lesion can be confused with malignancy. However, it exhibits a number of key radiographic and histological features, which differentiate it from other benign and malignant processes. It has a strong propensity for recurrence. However this can be decreased by excision of the pseudocapsule, underlying periosteum and removal of any abnormal cortical tissue beneath the lesion.     

Bizarre parosteal osteochondromatous proliferation and periosteal chondroma: a comparative report and review of the literature

Bizarre parosteal osteochondromatous proliferation and periosteal chondroma are rare, benign, bony lesions that may present in the hand. Bizarre parosteal osteochondromatous proliferation was first reported in the literature by Nora in 1983, and periosteal chondroma was first reported by Lichtenstein in 1952. This report provides a unique side-by-side comparison of these lesions, illustrating each with a clinical vignette. This report, coupled with a thorough review of the literature, serves to demonstrate that the history and physical exam characteristics, as well as the radiographic and gross appearances, are insufficient to differentiate between the two lesions. Histopathologic examination is required to confirm the diagnosis.     

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.     

A bizarre parosteal osteochondromatous proliferation (Nora's lesion) of metatarsus,a histopathological and etiological puzzlement

Nora's lesion (bizarre parosteal osteochondromatous proliferation) is a rare, benign lesion that is composed of differing amounts of cartilage, bone, and spindle cells and an unusual form of calcified cartilage so-called “blue bone”. Whether it represents a reactive proliferation or a neoplastic lesion still remains controversial. We present a 24-year-old woman having a 4.5 cm two lobulated mass attached to second metatarsus of her left foot. The lesion was hyperintense on magnetic resonance imaging and accompanied by an extensive soft tissue and bone marrow edema. In resection specimen, smaller lobule appeared stuck-on the cortex while the larger one had a broader base and a 0.4 cm cartilaginous cap-like formation. The histological picture was best fit to Nora's lesion however showed less fibroblastic tissue and cartilaginous pleomorphism. The lesion also showed areas with cortical invasion and a small focus of fracture callus accompanied by adjacent medullary edema and fat necrosis. The case is presented with the comparative radiologic, macroscopic and microscopic findings for its diagnostic difficulties and etiopathogenetic considerations in favour of a maturation phenomenon in parosteal ostecartilaginous lesions irrespective of the cause.     

Distinct chromosomal rearrangements in subungual (Dupuytren) exostosis and bizarre parosteal osteochondromatous proliferation (Nora lesion)

BACKGROUND: Proliferative lesions of the bone surface, such as subungual (Dupuytren) exostosis and bizarre parosteal osteochondromatous proliferation (BPOP, Nora lesion) are currently classified as reactive, proliferative processes that mimic primary neoplasms of bone. METHODS: Cytogenetic analysis was performed on 3 subungual exostoses of the great toe and 2 BPOP lesions of the radius and ulna. RESULTS: A balanced translocation t(X;6) was identified in all cases of subungual exostoses. The chromosomal rearrangements observed in 1 case of BPOP differed from those seen in subungual exostosis. CONCLUSIONS: The presence of chromosomal abnormalities in subungual exostosis and BPOP suggests that these lesions are neoplastic, with a different molecular pathogenesis, and that each is a distinct clinicopathologic entity.