Kidney tumor
Benign (usually) adult tumors
Solitary fibrous tumor

Author: Mandolin Ziadie, M.D.

Revised: 18 April 2018, last major update March 2012

Copyright: (c) 2003-2018,, Inc.

PubMed Search: "Solitary fibrous tumor" kidney

Cite this page: Ziadie, M.S. Solitary fibrous tumor. website. Accessed October 20th, 2018.
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, Am J Surg Pathol 2001;25:1194), well circumscribed
  • Slightly nodular, grayish tan firm cut surface with hemorrhage / cystic change
Gross images

Images hosted on other servers:

Various images

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

Various images malignant tumor

Entrapped renal tubules

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