Bone & joints
Other osteogenic tumors
Aggressive osteoblastoma


Topic Completed: 1 August 2013

Minor changes: 5 July 2019

Copyright: 2003-2019, PathologyOutlines.com, Inc.

PubMed Search: Aggressive osteoblastoma

Related topics: Osteoblastoma

David R. Lucas, M.D.
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Cite this page: Lucas DR. Aggressive osteoblastoma. PathologyOutlines.com website. http://www.pathologyoutlines.com/topic/boneosteoblastomaaggressive.html. Accessed September 29th, 2020.
Definition / general
  • Rare variant of osteoblastoma characterized by epithelioid osteoblasts, aggressive growth, propensity for local recurrence, yet no metastatic potential
  • Controversial tumor not recognized as a distinct entity by all investigators
Terminology
  • Epithelioid osteoblastoma, epithelioid multifocal osteoblastoma, malignant osteoblastoma
Sites
  • Various skeletal locations: vertebrae, sacrum, pelvis, long bones, skull, small bones of hands and feet
Diagnosis
  • Large epithelioid osteoblasts, locally aggressive behavior
Radiology description
  • Similar to conventional osteoblastoma, but often larger (<4 cm)
  • Osteolytic with sclerotic rim, often with areas of ossification
  • Secondary aneurysmal bone cyst in some
Radiology images

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Pelvic tumor

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Expansile tibial tumor with central nidus

Case reports
Treatment
  • En bloc resection when feasible
Gross description
  • Generally well demarcated expansile mass with rounded contours
  • Red, friable, gritty
  • Ossification and hemorrhage
  • Usually > 4 cm
Gross images

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Expansile, demarcated tibial tumor with central nidus and intralesional hemorrhage

Microscopic (histologic) description
  • Anastomosing bone trabeculae
  • Loose fibrovascular stroma
  • Large, epithelioid osteoblasts arranged in single cell layers and aggregates, which are twice the size of normal osteoblasts
  • Osteoblasts have abundant eosinophilic cytoplasm, eccentric vesicular nuclei with prominent nucleoli
  • Mitosis and necrosis usually not seen
Microscopic (histologic) images

AFIP images
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Various images



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Sheet of epithelioid osteoblasts

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Immature trabeculae with osteoblastic rimming

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Zonation of bone formation

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Epithelioid multifocal pattern

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Sheets of large, epithelioid osteoblasts

Molecular / cytogenetics description
Electron microscopy description
  • Slightly older age group than conventional osteoblastoma, third - fourth decade
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