Kidney tumor
Benign adult tumors
Solitary fibrous tumor
Author: Mandolin S. Ziadie, M.D.
Topic Completed: 1 March 2012
Minor changes: 26 February 2021
Copyright: 2003-2021, PathologyOutlines.com, Inc.
PubMed Search: "Solitary fibrous tumor" kidney
Table of Contents
Definition / general | Epidemiology | Clinical features | Case reports | Treatment | Gross description | Gross images | Microscopic (histologic) description | Microscopic (histologic) images | Positive stains | Negative stains | Electron microscopy description | Differential diagnosisCite this page: Ziadie MS. Solitary fibrous tumor. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/kidneytumorsolitary.html. Accessed March 4th, 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
Epidemiology
- Rare in kidney, arises from serosal surfaces of pleura and other sites
Clinical features
- May be associated with hypoglycemia (Eur Urol 2009;55:739, Ann Thorac Surg 2007;84:292)
Case reports
- 26 year old man with solitary fibrous tumor of the right kidney (Can J Urol 2007;14:3583)
- 39 year old woman with giant (20 cm) tumor (Hinyokika Kiyo 2010;56:435)
- 48 year old woman with capsular tumor (Am J Surg Pathol 1996;20:1288)
- 50 year old woman with malignant component (Diagn Pathol 2011;6:96)
- 52 year old woman with large solitary fibrous tumor of the right kidney (Urol Ann 2011;3:158)
- 76 year old man with malignant tumor (Arch Pathol Lab Med 2006;130:857)
- 85 year old woman with renal hilar mass (Arch Pathol Lab Med 2006;130:117)
Treatment
- 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
- CD34, bcl2 and CD99 (these three confirm the diagnosis)
- Also vimentin, type IV collagen
Negative stains
- Cytokeratin, S100, p53, CD117, muscle markers and melanocytic markers
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
- Cellular mesoblastic nephroma:
- Congenital tumor of myofibroblasts with thin collagen fibers
- Smooth muscle actin+; has t(12;15)
- Fibroepithelial polyp of renal pelvis:
- Very rare, smooth glistening external surface, polyp covered by urothelium
- Collagen is present but is not a tumor of spindle cells
- Fibroma:
- No dense collagen
- Usually not CD34+, bcl2+ or CD99+
- Fibrosarcoma (on needle biopsies):
- Storiform pattern of atypical spindle cells
- Gastrointestinal stromal tumor:
- Kidney is a very unusual site, no dense collagenous bands
- CD117+
- Inflammatory myofibroblastic tumor:
- Neurofibroma:
- CD99-, CD34-, bcl2- (J Cancer Res Ther 2010;6:388)
- Sarcomatoid renal cell carcinoma:
- Infiltrative, atypical spindle cells, usually typical renal cell carcinoma component also present
- Keratin+ or vimentin+
- Smooth muscle tumor:
- Spindle cells have smooth muscle features, usually no dense collagen
- Positive for muscle markers
- Synovial sarcoma:
- Infiltrative, more atypical spindle cells
- CD99+ but CD34-
