Elsevier

Human Pathology

Volume 25, Issue 11, November 1994, Pages 1234-1237
Human Pathology

Original contribution
Exophytic variant of fibrous dysplasia (fibrous dysplasia protuberans)

https://doi.org/10.1016/0046-8177(94)90041-8Get rights and content

Abstract

Two cases of an exophytic variant of fibrous dysplasia (fibrous dysplasia protuberans) are reported in which the lesions protruded far beyond the normal bone contour mimicking surface lesions of bone. The first case was an 18-year-old man who had a pedunculated calcified mass of the sixth rib in association with radiologically diagnosed fibrous dysplasia of the skull. The second case was a 33-year-old man who had an exophytic lesion of the proximal tibia. Both of these patients were shown to have benign fibro-osseous lesions consistent with fibrous dysplasia. The intramedullary portions of the host bone adjacent to the exophytic masses also were involved by the fibro-osseous lesions and this fact suggests that the lesions may arise eccentrically in the medullary spaces and mainly grow outwards. It is important to be aware that fibrous dysplasia occasionally presents as an excrescence on the surface of bone. Careful radiographic and histological correlation is required to make a correct diagnosis of this rare variant of fibrous dysplasia.

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    Assessment of amplification of MDM2 by fluorescence in-situ hybridization can be helpful in that parosteal OSA is often positive, and protuberant fibro-osseous lesion is negative.6 FD is distinguished from protuberant fibro-osseous lesion by virtue of its intramedullary location and configuration of the lesional bone.19 Ossifying fibroma (OF) is a benign fibro-osseous neoplasm that affects the craniofacial skeleton.3

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    They are MDM2 positive by IHC and show MDM2 amplification. FD is an intramedullary expansile mass and has only rarely been described to expand beyond the cortical surface (FD protuberans).56 Osteoma typically shows dense bone deposition with only scant loose fibrovascular tissue.

  • Histopathology of fibro-osseous and cystic tumors of bone

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    They often harbor MDM2 positivity by IHC and MDM2 amplification by FISH. Fibrous dysplasia is an intramedullary expansile mass and has only rarely been described to expand beyond the cortical surface (fibrous dysplasia protuberans).63 Osteoma typically shows dense bone deposition with only scant loose fibrovascular tissue.

  • Minute mesenchymal chondrosarcoma within osteochondroma: an unexpected diagnosis confirmed by HEY1-NCOA2 fusion

    2018, Human Pathology
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    The nature of the exophytic bony structure that contained MCS deserves discussion. Although we initially considered the possibility of a protuberant growth of sarcoma tissue that originated in the eccentric portion of the parent bone, akin to fibrous dysplasia protuberans [8] or enchondroma protuberans [9], this theory seems unlikely because the MCS was restricted to the apical site of this exophytic growth, with the medullary cavity of the parent rib and the neck tissue of the excrescence being spared (Fig. 2A). Periosteal MCS was another differential diagnosis; however, periosteal MCS grows on the surface of the cortex [3], and the findings of the present case (ie, a clear cortical and medullary continuity, illustrated in Figs. 1D and I and 2A) did not support such a designation.

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Dr Ishida is a visiting research fellow at Montefiore Medical Center supported by the Japan Society for the Promotion of Science, Postdoctoral Fellowships for Research Abroad, Tokyo, Japan.

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