Colon tumor
Mesenchymal tumors
Solitary fibrous tumor

Author: Raul S. Gonzalez, M.D. (see Authors page)

Revised: 8 September 2017, last major August 2017

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

PubMed search: Colonic solitary fibrous tumor

Cite this page: Gonzalez, R. S. Solitary fibrous tumor. website. Accessed December 11th, 2018.
Definition / general
  • Mesenchymal tumor that can very rarely involve the gastrointestinal tract
Essential features
  • Mesenchymal lesion of variable malignant potential
  • Positive for CD34 and STAT6
  • Formerly also called "hemangiopericytoma"
ICD coding
  • D21.9
  • Cases involving colon almost always arise in mesentery and involve intestine secondarily
  • Much more common in other sites; see lung and soft tissue topics
Clinical features
  • Usually presents as a pelvic / retroperitoneal mass but may rarely arise as a colon polyp
Prognostic factors
Case reports
Gross description
  • Firm, solid lesion
Gross images

Images hosted on other servers:

Tan-white mass arising from
serosal surface of sigmoid colon

Microscopic (histologic) description
  • Spindle cells arranged in a "patternless pattern" with collagenous background
  • Staghorn vessels throughout, particularly at periphery
  • Atypical / malignant features include increased cellularity, nuclear atypia, mitotic activity and necrosis (Am J Surg Pathol 1998;22:1501)
Microscopic (histologic) images

Images hosted on PathOut server, contributed by Dr. Raul S. Gonzalez, University of Rochester Medical Center (USA):

Low power

Intermediate power

Increased cellularity

Mitotic activity

Positive stains
Negative stains
Molecular / cytogenetics description
  • NAB2-STAT6 gene fusion (not demonstrated in colon case reports but likely present)
Differential diagnosis
Board review question #1
Which of the following immunohistochemical stains can reliably distinguish gastrointestinal stromal tumor from solitary fibrous tumor?

A. CD34
B. CD168
C. Desmin
E. Vimentin
Board review answer #1