Bone
Osteosarcoma
Well differentiated intramedullary osteosarcoma

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

Revised: 23 November 2016, last major update August 2013

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

PubMed Search: Well differentiated intramedullary osteosarcoma
Cite this page: Well differentiated intramedullary osteosarcoma. PathologyOutlines.com website. http://www.pathologyoutlines.com/topic/bonewelldifferentiated.html. Accessed December 6th, 2016.
Definition / General
  • Very rare; also called low grade osteosarcoma, intraosseous osteosarcoma
  • Usually adults, femur and tibia
  • Excellent prognosis, but 15% eventually develop conventional (high grade) osteosarcoma
Radiology Description
  • Large lesions with cortical destruction and extraosseous extension
  • Much of tumor is well circumscribed, with a focally aggressive growth pattern
Radiology Images

Images hosted on Pathout server:

Distal femoral metaphysis

Part of cortex destroyed

Metaphysis and epiphysis of tibia

Gross Description
  • Firm, fibrous, no fish - flesh appearance
Gross Images

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Proximal portion of humerus

Medullary cavity

Micro Description
  • So bland that appears benign but invades bone and soft tissue
  • Hypocellular spindle cells with mild atypia, marked collagen production
  • Variable osteoid production
  • No/rare mitotic figures
Micro Images

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Markedly pleomorphic osteoblasts

Focal osteoid formation

Neoplastic osteoblasts

Heavily calcified osteoid

Conventional intramedullary osteosarcoma


Low grade cartilaginous differentiation

"Herringbone" pattern

Spindled, fibroblast-like tumor cells

Minimal osteoid deposition

Dense osteoid surrounds blood vessel


Treated conventional osteosarcoma

Amorphous deposits of osteoid in stroma

Mature - appearing bone

Broad trabeculae of bone

Molecular / Cytogenetics Description
  • Usually diploid
Differential Diagnosis