Thyroid & parathyroid
Benign thyroid neoplasms
Solitary fibrous tumor

Topic Completed: 1 September 2014

Minor changes: 27 January 2021

Copyright: 2014-2021,, Inc.

PubMed Search: solitary fibrous tumor thyroid

Sheren Younes, M.D.
Page views in 2020: 401
Page views in 2021 to date: 85
Cite this page: Younes S. Solitary fibrous tumor. website. Accessed March 4th, 2021.
Definition / general
  • Uncommon spindle cell neoplasm at this site, usually with benign behavior
  • See also Soft tissue tumor chapter
Clinical features
  • Presents as thyroid mass
  • Overall most common site is pleura
  • Affects adults with mean age 52 years, female predominence
Prognostic factors
  • Benign but aggressive behavior when high cellularity, atypia, 4/10 HPF mitosis, tumor necrosis, infiltrating margin (Am J Surg Pathol 1998;22:1501)
Case reports
  • Surgical excision
Gross description
  • Usually large, well circumscribed, solid, whitish grey
Gross images

Images hosted on other servers:

Solid, well circumscribed white nodule

Microscopic (histologic) description
  • Variably cellular
  • Well circumscribed borders, may be jagged with thyroid infiltration
  • Patternless pattern, hemangiopericytoma pattern
  • Hypo and hypercellular areas, myxoid stroma
  • Bland looking spindle cells
  • Delicate fibrous stroma
Microscopic (histologic) images

Images hosted on other servers:

Whorled arrangement

CD34, BCL2, CD99, Ki67

BCL2, CD34, CD99, vimentin

Cytology description
  • Variable cellularity
  • Discohesive spindle cells, elongated cytoplasmic processes, fusiform nuclei
  • Collagenized stroma (Diagn Cytopathol 2003;28:213)
Positive stains
Electron microscopy description
  • Fibroblasts
Differential diagnosis
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