Encyclopedia of Pathology

Living Edition
| Editors: J.H.J.M. van Krieken

Renal Mixed Epithelial and Stromal Tumor

  • Anna Caliò
  • Diego Segala
  • Guido MartignoniEmail author
Living reference work entry
DOI: https://doi.org/10.1007/978-3-319-28845-1_4925-1



Renal mixed epithelial and stromal tumor is an uncommon complex biphasic neoplasm which occurs in adults.

Clinical Features

  • Incidence

    The tumor comprises less than 1% of all renal neoplasms.

  • Age

    The mean age is around 50 years.

  • Sex

    There is a striking female predominance. The tumors are related to hormonal factors (Adsay et al. 2000).

  • Site

    There is no site predominance.

  • Treatment

    It is typically cured by nephrectomy.

  • Outcome

    Renal mixed epithelial and stromal tumor is an indolent tumor, although malignant transformation has been reported with a morphology resembling stromal sarcoma and carcinosarcoma (Svec et al. 2001).


The tumor is a solid or solid and cystic mass.


It is mainly composed of stroma with a variable amount of cysts. The stromal component varied from paucicellular fibrous tissue to markedly cellular areas sometimes resembling ovarian stroma. Condensation of hypercellular stroma around cysts is a common finding. Smooth muscle stroma, adipose tissue, and a prominent vascularity with or without thick-wall vessels are also common. The epithelium is heterogeneous in architecture and in cell type. A broad variety of glands has been reported: tiny crowded glands, branching tubules, and medium-small cysts containing eosinophilic material reminiscent of thyroid follicles are the most common features. Many tumors have complex architecture with spatulate papillae or leaflet-like structures reminiscent of phyllodes tumor and complex papillary structures (Fig. 1). Round glands lined by tall cuboidal epithelium and nephrogenic adenoma-like glands are also on record. When the cysts are present, they are lined by flat, cuboidal, or hobnail cells. Less common types of epithelium are ciliated cells, clear cells, and endometrioid glands (Caliò et al. 2016).
Fig. 1

A complex architecture with spatulate papillae or leaflet-like structures resembling the phyllodes tumor


The immunophenothype is characterized by the positive reaction in the stromal component for smooth muscle actin, desmin, estrogen and progesterone receptor, and no staining for inhibin. Nuclear labeling for PAX8 is described in the epithelial component.

Molecular Features

It has been reported the association between primary hyperparathyroidism and jaw tumor syndrome (HRPT2 mutation gene) and mixed epithelial and stromal tumor. Gene expression profiles have demonstrated that mixed epithelial and stromal tumors and cystic nephromas clustered together and separated from other renal tumors. Nonrandom X chromosome inactivation (clonal pattern) has been demonstrated in both epithelial and stromal component by using HUMARA.

Differential Diagnosis

The main differential diagnosis is cystic nephroma. Because they share some features, some pathologists hypothesized that they represent the opposite ends of the same spectrum proposing the unifying term mixed epithelial and stromal tumor family according to the World Health Organization (WHO) 2016 (Turbiner et al. 2007).

References and Further Readings

  1. Adsay, N. V., Eble, J. N., Srigley, J. R., et al. (2000). Mixed epithelial and stromal tumor of the kidney. The American Journal of Surgical Pathology, 24, 958–970.CrossRefGoogle Scholar
  2. Caliò, A., Eble, J. N., Grignon, D. J., & Delahunt, B. (2016). Mixed epithelial and stromal tumor of the kidney: A Clinicopathologic Study of 53 cases. The American Journal of Surgical Pathology, 40, 1538–1549.CrossRefGoogle Scholar
  3. Moch, H., Humprey, PA., Ulbright, TM., et al. (2016) WHO Classification of Tumours of the Urinary System and Male Genital Organs. Lyon.Google Scholar
  4. Svec, A., Hes, O., Michal, M., et al. (2001). Malignant mixed epithelial and stromal tumor of the kidney. Virchows Archive, 439, 700–702.CrossRefGoogle Scholar
  5. Turbiner, J., Amin, M. B., Humphrey, P. A., et al. (2007). Cystic nephroma and mixed epithelial and stromal tumor of kidney: a detailed clinicopathologic analysis of 34 cases and proposal for renal epithelial and stromal tumor (REST) as a unifying term. The American Journal of Surgical Pathology, 31, 489–500.CrossRefGoogle Scholar

Copyright information

© Springer Nature Switzerland AG 2019

Authors and Affiliations

  1. 1.Department of Diagnostic and Public Health, Section of PathologyUniversity of VeronaVeronaItaly
  2. 2.Department of PathologyPederzoli HospitalPeschiera del GardaItaly