Kidney tumor
Childhood tumors
Metanephric stromal tumor
Author: Mandolin S. Ziadie, M.D.
Topic Completed: 1 December 2011
Minor changes: 10 December 2020
Copyright: 2003-2019, PathologyOutlines.com, Inc.
PubMed Search: "Metanephric stromal tumor" kidney
Table of Contents
Definition / general | Epidemiology | Treatment | Gross description | Microscopic (histologic) description | Positive stains | Negative stains | Differential diagnosisCite this page: Ziadie MS. Metanephric stromal tumor. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/kidneytumormetastromal.html. Accessed January 18th, 2021.
Definition / general
- Benign spindle cell neoplasm of pediatric kidney composed of bland spindled cells that entrap native kidney
- Similar to and often misdiagnosed as mesoblastic nephroma
- May be related to Wilms tumor (Clin Lab Med 2005;25:379)
Epidemiology
- Usually occurs in children with a mean age of 2 years (Am J Surg Pathol 2000;24:917)
Treatment
- Excision is curative
Gross description
- Fibrous lesion centered in renal medulla containing smooth walled cysts; mean 5.5 cm
Microscopic (histologic) description
- Nodular low power appearance
- Identical to stromal component of metanephric adenofibroma
- Bland spindle cells with thin, tapered and hyperchromatic nuclei and indistinct cytoplasm (may have epithelioid areas) that entrap native kidney, usually undermine calyceal or pelvic urothelium and may entrap nerves
- Nonencapsulated with a scalloped border with renal cortex
- Hypo and hypercellular areas with onion skin cuffing around entrapped renal tubules
- Stroma may show glial, cartilaginous or neuroblastic differentiation
- Angiodysplasia of entrapped arterioles
- May show juxtaglomerular cell hyperplasia in entrapped glomeruli
- No vascular invasion, no mitotic figures
Negative stains
- Smooth muscle actin, muscle specific actin, desmin, keratin and EMA (but entrapped tubules are positive), CD117 / c-kit and low Ki67 index
Differential diagnosis
- Clear cell sarcoma: regular branching capillary vascular pattern, no heterologous differentiation, CD34-
- Mesoblastic nephroma: classic variant has whorls and fascicles, metaplastic and dysplastic elements common, actin+, desmin+, CD34-
- Metanephric adenofibroma: neoplastic epithelium, no entrapped tubules
