Kidney tumor
Benign (usually) adult tumors
Mixed epithelial and stromal tumor

Author: Mandolin Ziadie, M.D.

Revised: 18 April 2018, last major update February 2012

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

PubMed Search: Mixed epithelial and stromal tumor [title] kidney

Cite this page: Ziadie, M.S. Mixed epithelial and stromal tumor. website. Accessed June 24th, 2018.
Definition / general
  • Rare; almost exclusively occurs in perimenopausal women with obesity or receiving exogenous hormones, or men treated with lupron or DES (Am J Surg Pathol 2000;24:958)
Clinical features
  • Usually benign; does not recur / metastasize
Case reports
Gross description
  • Well circumscribed but unencapsulated tumor in renal pelvis
  • Mean 6 cm, range 3 - 12 cm, solid and cystic and yellowish tan
Gross images

Images hosted on other servers:

Various images

Various images

Multiloculated cystic tumor with smooth cyst lining

Microscopic (histologic) description
  • Cystic and solid growth of benign mesenchymal and epithelial elements in ovarian-type stroma that contains smooth muscle, fibroblasts and myofibroblasts with embedded epithelial structures (tubules and cysts)
  • Cysts often have hobnailed epithelium
  • No blastema, no immature epithelial elements and no atypia
  • Classic: no hemorrhage, no necrosis and no / rare mitotic figures
  • Cellular: increased stromal cellularity, may have hemorrhage, necrosis and high mitotic index
Microscopic (histologic) images

Images hosted on PathOut server:

Spindled myofibroblastic
stromal component
with tubular elements

Case of the Week #83:

Various Images

Left to right: AE1 / AE3, ER, PR

Images hosted on other servers:

Various images

Stromal predominant tumor

Positive stains
Negative stains
Electron microscopy description
  • Spindle cells have mitochondria, ribosomes and submembranous condensations composed of clusters of filaments
  • Also basement membrane, abundant collagen fibers, dense plaques, pinocytotic vesicles and nearly continuous external lamina
  • Rare endoplasmic reticulum
Differential diagnosis