Bone & joints

Other chondrogenic tumors

Bizarre parosteal osteochondromatous proliferation

Last author update: 1 August 2013
Last staff update: 12 May 2023 (update in progress)

Copyright: 2003-2023,, Inc.

PubMed Search: Bizarre parosteal osteochondromatous proliferation

Nat Pernick, M.D.
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Cite this page: Pernick N. Bizarre parosteal osteochondromatous proliferation. website. Accessed September 21st, 2023.
Definition / general
  • Also called Nora lesion
  • Rare form of myositis ossificans, resembles subungual (Dupuytren’s) exostosis, except for t(X;6) in the latter (Am J Surg Pathol 2004;28:1033)
  • 75% affect small tubular bones of hands and less commonly the feet; do not involve the nailbeds
  • 25% affect large bones
  • Usually ages 20 - 39 years
Radiology description
  • Hands: heavily calcified mass attached to underlying cortex / periosteum but not continuous with it (so not an osteochondroma)
  • Long bones: lesions may be destructive or in soft tissue
  • Benign but may recur locally (35 - 54%)
Radiology images

Contributed by Mark R. Wick, M.D.

Various images

  • Surgical excision with wide margins
Case reports
Gross description
  • Resembles small osteochondroma
Microscopic (histologic) description
  • Irregular maturation of cartilage in bone produces chondro-osteoid with characteristic blue quality (“blue bone”)
  • Contains enlarged, bizarre, binucleated chondrocytes with maturation into bone
  • Spindle cell proliferation between bony trabeculae without atypia
Microscopic (histologic) images

Contributed by Mark R. Wick, M.D.
Missing Image

Various images

Missing Image

Nora lesion foot

Molecular / cytogenetics description
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