Soft tissue
Fibroblastic / myofibroblastic
Solitary fibrous tumor

Topic Completed: 1 June 2013

Minor changes: 25 February 2021

Copyright: 2003-2021,, Inc.

PubMed Search: Solitary fibrous tumor [title] soft tissue

Jerad M. Gardner, M.D.
Page views in 2020: 36,674
Page views in 2021 to date: 7,674
Cite this page: Gullett A, Gardner JM. Solitary fibrous tumor. website. Accessed February 27th, 2021.
Definition / general
  • Fibroblast like cells with patternless pattern, thick bands of collagen and prominent branching, hyalinized vessels
  • Similar to pleural solitary fibrous tumor
  • Lesions formerly referred to as "hemangiopericytoma" of soft tissue are probably best classified as solitary fibrous tumor
  • See also discussion in CNS, eye, kidney tumor, pleura and thyroid gland chapters
Clinical features
  • Usually middle aged adults (median age 50 years)
  • Wide anatomic distribution; essentially arises from any soft tissue or visceral location
  • Rarely causes paraneoplastic hypoglycemia due to insulin-like growth factor production
  • Slow growing painless mass, usually benign; histologically malignant tumors may be grossly infiltrative and 15 - 20% may metastasize; rarely histologically benign tumors metastasize
Prognostic factors
  • Poor prognostic factors: size > 10 cm, > 4 mitoses/10 HPF, cellular atypia, positive margins, malignant histology (Cancer 2002;94:1057), although histology may have less significance in retroperitoneum (Urol Oncol 2008;26:254)
Case reports
Clinical images

Contributed by Mark R. Wick, M.D.


Gross description
  • Well circumscribed, nonencapsulated or partially encapsulated, solitary, lobulated masses that measure 5 - 8 cm on average with multinodular, white, firm cut surface
  • Necrosis and infiltrative margins are associated with locally aggressive or malignant tumors
Gross images

Images hosted on other servers:

Tumor of omentum

Microscopic (histologic) description
  • Patternless architecture of hypo and hypercellular areas separated by thick, hyalinized collagen with cracking artifact and staghorn vessels
  • Perivascular sclerosis
  • Bland and uniform oval to spindle cells dispersed along thin parallel collagen bands, cells have minimal cytoplasm, small elongated nuclei and indistinct nucleoli
  • Some have myxoid change (Virchows Arch 2009;454:189), mast cells, adipose tissue or multinucleated giant cells
  • Minimal pleomorphism
  • No atypia, no / rare mitotic figures
  • Malignant SFT: hypercellular, moderate to marked atypia and nuclear pleomorphism, hyperchromasia, tumor necrosis, 4+ mitotic figures/10 HPF including atypical mitoses, infiltrative borders
Microscopic (histologic) images

AFIP images

Moderately cellular fibroblastic appearance

Parallel arrays of collagen are separated by fibroblastic nuclei

Scant cytoplasm and uniform
spindled nuclei, note the thin bands
of intercellular collagen

Case #29

Dermis images

Contributed by Mark R. Wick, M.D.

Storiform growth

Staghorn blood vessels

Skin lesions

Various images

Images hosted on other servers:

"Patternless" growth pattern

Partly "neural-like" tumor cells


Epithelioid nodules near fusocellular areas

Biphasic pattern

Round, polygonal cells

CD34 and BCL2

Positive stains
Negative stains
Electron microscopy description
  • Myofibroblasts, fibroblasts
Molecular / cytogenetics description
  • Cytogenetic abnormalities in most tumors 10 cm or larger; no consistent genetic event
Differential diagnosis
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