Bone
Cartilaginous tumors other than chondrosarcoma
Osteochondroma

Author: Nat Pernick, M.D. (see Authors page)

Revised: 30 November 2016, last major update August 2013

Copyright: (c) 2003-2016, PathologyOutlines.com, Inc.

PubMed Search: Osteochondroma[title]
Cite this page: Osteochondroma. PathologyOutlines.com website. http://www.pathologyoutlines.com/topic/boneosteochondroma.html. Accessed December 6th, 2016.
Definition / General
  • Also called exostosis
  • Most common benign bone tumor
  • 50 - 75% males, mean age 10 years, usually age 20 years or less
  • Common; solitary or multiple
  • Slow growing, painful if impinges on nerve or stalk is broken; usually stops growing and ossifies at puberty
  • Benign, but 1 - 2% of solitary tumors and 5 - 25% of multiple tumors undergo malignant transformation to chondrosarcoma
  • May be neoplastic, due to mutations in EXT1 and EXT2 polymerases that add heparan sulfate to proteoglycans and appear to be tumor suppressor genes
  • Secondary chondrosarcoma: if grows during adolescence, > 8 cm, irregular cartilaginous cap > 3 cm or lucent zones within lesion, invasion of surrounding tissue
  • Multiple hereditary exostosis: also called osteochondromatosis; autosomal dominant disorder, abnormalities of 8q24.1, 11p11 - 12, 19; diagnosed during childhood; may see bowing of underlying bones, retarded growth; may have wide metaphyses; 0.5 to 5% of patients have evolution to chondrosarcoma
  • Sites: metaphysis, not medullary cavity; usually distal femur, proximal tibia, proximal humerus; occasionally pelvis, scapula, ribs; rarely digits; not in intramembranous bones
Radiology Description
  • Metaphyseal lesions grow in direction opposite to adjacent joint
  • Cortex and medulla are continuous with underlying bone
Radiology Images

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Distal portion of femur

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Metatarsal xray - contributed by Dr. Mark R. Wick

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Xray - contributed by Dr. Mark R. Wick



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Osteochondroma

Case Reports
Gross Description
  • Cartilage - capped bony outgrowth up to 10 cm (mean 4 cm), attached to skeleton by bony stalk, not in medullary cavity
  • May have bursa around its head
  • Cartilage cap usually regular and thin
Gross Images

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Outer and cut surfaces

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Contributed by Dr. Mark R. Wick

Micro Description
  • Periosteum appears as pink fibrous capsule
  • Cartilage resembles disorganized growth plate with ossification towards base
  • Medullary cavity merges with that of underlying bone
  • Bony trabeculae appear normal
  • Normal appearing marrow
  • No spindle cells
Micro Images

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Whole mount section

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Cellular cartilaginous foci

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Junction of cartilage cap and underlying bone

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Metatarsal - contributed by Dr. Mark R. Wick

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Contributed by Dr. Mark R. Wick



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Iliac crest Xray; CT; gross; H&E

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Osteosarcoma arising in osteochondroma

Differential Diagnosis