Prostate
Other malignancies
Solitary fibrous tumor

Author: Kenneth Iczkowski, M.D. (see Authors page)

Revised: 4 August 2017, last major update August 2017

Copyright: (c) 2003-2017, PathologyOutlines.com, Inc.

PubMed Search: Prostate solitary fibrous tumor
Cite this page: Solitary fibrous tumor. PathologyOutlines.com website. http://pathologyoutlines.com/topic/prostatesft.html. Accessed October 19th, 2017.
Definition / general
  • Often misdiagnosed
  • Usually does not recur after excision (Hum Pathol 2000;31:63) but some cases have malignant behavior
Epidemiology
  • Rare
  • About 30 cases reported
Sites
  • Tumor may originate from periprostatic tissues and involve the prostate or it may originate from Denonvilliers (rectoprostatic) fascia (J Urol 2002;168:1490)
Clinical features
Prognostic factors
  • Completeness of resection predicts outcome
  • Mitotic rate, necrosis and atypia are the 3 factors distinguishing malignant from benign SFT
Case reports
Treatment
  • Prostatectomy, cystoprostatectomy if necessary, pelvic exenteration
  • Follow up only if the lesion is non palpable and in older men
Gross description
  • Frequently large size of 8 - 15 cm
Gross images

Images hosted on other servers:

Resected prostatic tumor

Well defined, whitish mass with necrosis

Microscopic (histologic) description
  • "Patternless" pattern, collagenization, hemangiopericytoma-like vascular pattern, spindled cells between strips of dense hyalinized deposits
  • Mitotic rate ranges from none to many
  • Two cases described were:
    • Well circumscribed, minimal mitotic activity or pleomorphism
    • Cellular, less collagenous, more diffuse growth pattern, cytologic atypia and high mitotic activity (Arch Pathol Lab Med 2001;125:274)
Microscopic (histologic) images

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Missing Image

Well circumscribed tumor displacing the prostate

Microscopic findings of prostatic biopsy

Prostatic SFT: histological aspects

H&E, CD30 and bcl2 staining

Histopathological and immunohistological analysis

Positive stains
Negative stains
Molecular / cytogenetics description
  • NAB2-STAT6 gene fusion is characteristic of prostatic and other SFTs by sequencing genomic DNA (Am J Pathol 2014;184:732)
Differential diagnosis
Board review question #1
    Which of the following features does not support a diagnosis of solitary fibrous tumor of the prostate?

  1. Apparent origin in the posterior prostatic fascia with secondary prostatic involvement
  2. CD34 positivity
  3. Cytokeratin positivity
  4. Large size
  5. Wire-like hyalinized deposits and hemangiopericytoid vessels
Board review answer #1
C. Cytokeratin positivity suggests sarcomatoid carcinoma.