Kidney tumor
Benign adult tumors
Solitary fibrous tumor

Topic Completed: 1 March 2012

Minor changes: 15 March 2021

Copyright: 2003-2021,, Inc.

PubMed Search: "Solitary fibrous tumor" kidney

Mandolin S. Ziadie, M.D.
Page views in 2020: 1,151
Page views in 2021 to date: 561
Cite this page: Ziadie MS. Solitary fibrous tumor. website. Accessed May 16th, 2021.
Definition / general
  • Benign (90%) tumor of patternless or storiform spindle cells with bland nuclear features, mixed with dense collagen
  • See also Soft tissue tumor chapter
  • Rare in kidney, arises from serosal surfaces of pleura and other sites
Clinical features
Case reports
  • Excision
  • Almost always benign behavior
Gross description
  • Large (up to 14 cm), well circumscribed (Am J Surg Pathol 2001;25:1194)
  • Slightly nodular, grayish tan firm cut surface with hemorrhage / cystic change
Gross images

Images hosted on other servers:

Nodular surface

Focal cystic areas
and homogeneous
pale brown areas

Cut section

34 year old man

Malignant tumor

Microscopic (histologic) description
  • Patternless, hemangiopericytomatous or storiform pattern of bland spindle cells mixed with dense collagenous bands that may entrap renal tubules
  • Variable lymphoplasmacytic infiltrate, variable myxoid change
  • Usually no necrosis, no cystic change and no mitotic figures
Microscopic (histologic) images

Images hosted on other servers:

Patternless pattern of bland spindle cells

Malignant tumor with atypia and mitotic figures

Left: CD34+, right: vimentin

Top to bottom: CD34+, CD99+, Ki67

Positive stains
Negative stains
Electron microscopy description
  • Fibroblast-like cells (irregular nuclei, prominent Golgi, branching rough endoplasmic reticulum, variable mitochondria and intermediate filaments, no thin filaments with focal densities, no tonofilaments and no cell-cell junctions)
  • No myoepithelial or epithelial differentiation
Differential diagnosis
Back to top
Image 01 Image 02