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| ==Osteochondroma== | | ==Osteochondroma== |
| ===General===
| | {{Main|Osteochondroma}} |
| *Benign.
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| *Very common.
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| *Abnormal outgrowth of bone and cartilage - associated with growth plate.
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| *Usually present before age 20.<ref name=pmid12873205>{{Cite journal | last1 = Parkin | first1 = B. | last2 = Bennett | first2 = JC. | last3 = Zaher | first3 = A. | title = Pathologic quiz case: an iliac mass in a 25-year-old woman. Osteochondroma. | journal = Arch Pathol Lab Med | volume = 127 | issue = 8 | pages = e355-6 | month = Aug | year = 2003 | doi = 10.1043/1543-2165(2003)127e355:PQCAIM2.0.CO;2 | PMID = 12873205 | URL = http://www.archivesofpathology.org/doi/full/10.1043/1543-2165%282003%29127%3Ce355:PQCAIM%3E2.0.CO;2}}</ref>
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| ===Gross===
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| Features:
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| *Metasphyseal lesions.<ref name=medpath>URL: [http://www.medpath.info/MainContent/Skeletal/Bone_07.html http://www.medpath.info/MainContent/Skeletal/Bone_07.html]. Accessed on: 18 September 2012.</ref>
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| **Often distal femur, proximal humerus or proximal tibia.<ref name=pmid12873205/>
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| **Occasionally iliac mass.<ref name=pmid22217414>{{Cite journal | last1 = Kokavec | first1 = M. | last2 = Gajdoš | first2 = M. | last3 = Džupa | first3 = V. | title = [Osteochondroma of the iliac crest: case report]. | journal = Acta Chir Orthop Traumatol Cech | volume = 78 | issue = 6 | pages = 583-5 | month = | year = 2011 | doi = | PMID = 22217414 }}
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| </ref>
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| *Mushroom-like shape - with broad or narrow base.
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| Note:
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| *Very unusual in craniofacial bones.<ref name=pmid12873205/>
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| ===Microscopic===
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| Features:<ref name=pmid12873205/>
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| *Bone - forms base of "mushroom".
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| *Cartilage - layer usu. thinner in older individuals.
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| **Lobular arrangement<ref name=upmc_case341>URL: [http://path.upmc.edu/cases/case341/dx.html http://path.upmc.edu/cases/case341/dx.html]. Accessed on: 19 September 2012.</ref> - clusters of 3-12 lacunae (separated by stroma).
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| **May have mild atypia.
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| **Nuclear enlargement - up to 5x normal.
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| *[[Perichondrium]] - covers the cartilage.
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| **Thin layer of cells - higher cellular density than cartilage.
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| ***Bland spindle cells in a fibrous (eosinophilic) stroma.
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| Notes:
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| *Benign cartilage - one chondrocyte per lacuna, small and round nucleus, no binucleation.
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| DDx:
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| *[[Chondrosarcoma]] - esp. in older individuals.
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| Images:
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| <gallery>
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| Image:Bone Osteochondroma LP CTR.jpg|Bone - Osteochondroma - low power (SKB)
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| Image:Bone Osteochondroma LP CTR (2).jpg|Bone - Osteochondroma - low power (SKB)
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| Image:Bone Osteochondroma HP CTR.jpg|Bone - Osteochondroma - high power (SKB)
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| Image:Bone Osteochondroma LP PA.JPG|Bone - Osteochondroma - low power (SKB)
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| Image:Bone Osteochondroma MP PA.JPG|Bone - Osteochondroma - medium power (SKB)
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| Image:Bone Osteochondroma MP2 PA.JPG|Bone - Osteochondroma - medium power (SKB)
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| </gallery>
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| *[http://path.upmc.edu/cases/case341.html Super rare intracranial mesenchymal osteochondroma - several images (upmc.edu)].<ref name=upmc_case341/>
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| ==Diffuse tenosynovial giant-cell tumour== | | ==Diffuse tenosynovial giant-cell tumour== |