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  • In summary we have established an animal model


    In summary, we have established an animal model of human NB bone metastasis in which COX-2/PGE2 plays a critical role. We provide pre-clinical data supporting the use of COX-2 inhibitors in the treatment of bone metastases in NB.
    Conflict of interest statement
    Introduction Desmoplastic fibroma (DF) is a rare, locally aggressive benign bone tumour with a reported incidence of 0.11% of all primary bone tumours [1,2]. It was initially described by Jaffe [3] in 1958 who highlighted the histological resemblance to aggressive fibromatosis (desmoid tumour). Numerous authors have subsequently attempted to clarify the histological criteria and, in 2013, the WHO described the microscopic appearance of desmoplastic fibroma as being composed of slender, spindle to stellate Anisomycin with minimal cytological atypia and abundant collagenous matrix [4]. Because of the infiltrative pattern of growth, desmoplastic fibroma was considered by some to be the osseous counterpart of extra-abdominal desmoid tumour [5], however, a recent study revealed that there were no mutations in exon 3 of CTNNB1, encoding for B-catenin, thus genetically distinguishing desmoplastic fibromas of bone from desmoid-type fibromatosis [6]. Local recurrence rates are between 37% and 72% [7–9] following operative intervention. Patients present typically with pain and swelling of the affected area. Plain radiographs reveal a trabeculated, lucent, expansile lesion often with lobulated margins [10]. Cortical thinning with breakthrough and a soft-tissue mass may also be seen [7]. Establishing a diagnosis is difficult by imaging studies alone [2] as many tumours resemble desmoplastic fibroma. The differential diagnosis includes benign lesions, such as fibrous dysplasia, simple bone cyst, aneurysmal bone cyst, non-ossifying fibroma, eosinophilic granuloma and chondromyxofibroma [2,7]. If cortical destruction and a soft tissue mass is noted, desmoplastic fibroma of bone may resemble more sinister pathology, such as fibrosarcoma, intra-osseous osteosarcoma and metastases [2,7].
    Results A search of our database, which holds prospectively gathered data on over 30,000 patients including 4692 benign bone tumours, identified 13 patients with desmoplastic fibroma of bone, giving an incidence of 0.003% in our population. There were 8 females (61.5%) and 5 males (38.5%). Mean age at presentation with symptoms was 25.9 years (range 5–50 years). Skeletal distribution of the lesions is shown in Fig. 1. All patients had been referred to our unit with suspicious plain radiographs following a history of pain/swelling of the affected body area and subsequently underwent magnetic resonance imaging and needle biopsy to confirm the diagnosis (Table 1). In total, local recurrence occurred in 2 (15.4%) patients in our series. There was a statistically significant association between local recurrence and the presence of an extra-osseous soft-tissue component (p<0.023).
    Discussion The aim of this study was to use a large database of patients with benign orthopaedic tumours in order to outline a management strategy for patients diagnosed with desmoplastic fibroma of bone and to discuss the criteria associated with local recurrence. Of the 4692 patients treated at our institute with a benign bone tumour over 30 years we found 13 had a diagnosis of desmoplastic fibroma of bone. Our unit has treated 1440 patients with osteosarcoma during the same period as we treated these patients with desmoplastic fibroma and it is known that the incidence of osteosarcoma is 2.5/million population per year [11]. Thus, the incidence of desmoplastic fibroma of bone is approximately 13/1440 of osteosarcoma i.e. a figure of 0.009/million population per year or approximately 1% of the reported incidence of osteosarcoma. This converts to an expected 2.5 cases of desmoplastic fibroma of bone for every 100 million population. The cross-sectional imaging features of desmoplastic fibroma have been described [2,9,12] as an osteolytic lesion with destruction of cortical bone, marginal sclerosis and pseudotrabeculation. The tumour shows low signal intensity on T1-weighted images with signal enhancement after the administration of contrast [2,9]. Cortical breakthrough was present in 23.1% of patients in our series, which is comparable to the study by Crim [13] who, after evaluating the radiographical features of desmoplastic fibroma in 83 published case reports, demonstrated cortical breakthrough in 29% of patients. We recommend magnetic resonance imaging (MRI) of the affected area to accurately delineate the extent of the tumour and it׳s relation to surrounding anatomical structures. Computed topography (CT) can supplement MRI and provide a more precise picture of the boney architecture so as to guide surgical management.