Cartilaginous tumors other than chondrosarcoma
Bizarre parosteal osteochondromatous proliferation

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

Revised: 16 August 2018, last major update August 2013

Copyright: (c) 2003-2018,, Inc.

PubMed Search: Bizarre parosteal osteochondromatous proliferation
Cite this page: Pernick, N. Bizarre parosteal osteochondromatous proliferation. website. Accessed December 15th, 2018.
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

Images hosted on PathOut server:

Contributed by Dr. Mark R. Wick:

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

Images hosted on PathOut server:

Contributed by Dr. Mark R. Wick:
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Various images

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Nora lesion foot

Images hosted on other servers:
Missing Image

Various images

Molecular / cytogenetics description