Kidney tumor
Benign adult tumors
Adult cystic nephroma

Editorial Board Member: Maria Tretiakova, M.D., Ph.D.
Editor-in-Chief: Debra L. Zynger, M.D.
Bonnie Choy, M.D.

Topic Completed: 9 February 2021

Minor changes: 25 February 2021

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PubMed Search: Cystic nephroma [title] kidney adult multilocular

Bonnie Choy, M.D.
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Cite this page: Choy B. Adult cystic nephroma. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/kidneytumorcysticnephroma.html. Accessed March 3rd, 2021.
Definition / general
  • Uncommon multilocular cystic tumor without a grossly appreciable solid component
  • Classified as part of mixed epithelial and stromal tumor (MEST) family with MEST at opposite end of spectrum, by the 2016 World Health Organization (WHO) Classification
Essential features
  • Mainly occurs in adult women
  • Well circumscribed, multicystic tumors with no apparent solid component
    • Versus MEST - variable solid and cystic components
  • Noncommunicating cysts lined by single layer epithelium separated by septa with hypocellular fibrous to hypercellular spindle cell stroma
  • Most benign but very rare local recurrence and malignant transformation
  • Stromal cells typically positive for ER / PR
Terminology
  • Renal epithelial and stromal tumor (REST) (Am J Surg Pathol 2007;31:489)
  • Multilocular cystic nephroma
  • Multilocular renal cyst (term not recommended, does not reflect neoplastic nature of entity)
ICD coding
  • ICD-O: 8959/0 - benign cystic nephroma
Sites
Etiology
Clinical features
  • Often incidentally found
  • Others present with abdominal / flank pain, hematuria, urinary tract infection, palpable mass (Urology 2008;71:1142)
Diagnosis
  • Diagnosis by histologic examination of tissue
Radiology description
  • Ultrasound (Urol Ann 2013;5:13, J Kidney Cancer VHL 2017;4:1):
    • Multiple anechoic spaces traversed by thin septa and without vascularity
    • Rarely, calcifications seen in septa
  • CT (Urology 2008;71:1142, Urol Ann 2013;5:13):
    • Well circumscribed, fluid density mass with multiple septations
    • Enhancement of septations following contrast but contrast does not accumulate within individual loculi and calcification may be seen
    • Most classified into Bosniak category III
  • MRI (Urol Ann 2013;5:13):
    • T1 hypointensity and T2 hyperintensity
Radiology images

Images hosted on other servers:
Ultrasound

Ultrasound

CT

CT

Prognostic factors
Case reports
Treatment
  • Nephron sparing surgery whenever feasible
Gross description
Gross images

Contributed by Bonnie Choy, M.D.
Well circumscribed, multicystic mass

Well circumscribed, multicystic mass

Multilocular cystic mass

Multilocular cystic mass

Microscopic (histologic) description
  • Many with at least a partial pseudocapsule
  • Entirely composed of cysts separated by septa (Semin Diagn Pathol 1998;15:2, Arch Pathol Lab Med 2004;128:1404, Am J Surg Pathol 2007;31:489, Eur Urol 2008;54:1237, Am J Surg Pathol 2016;40:1591)
  • Stroma:
    • Hypocellular to hypercellular
    • Collagenous and fibrous to edematous and myxoid
    • Areas of hyalinized stroma with contours resembling ovarian corpora albicantia
    • Spindle cells; closely packed areas resemble ovarian stroma
    • Cellular foci embedded with epithelial elements ranging from handful of cells with no lumen to tiny cysts with pinpoint lumens and to slightly larger cysts
    • Steroidogenic cells: small clusters of polygonal cells with amphophilic cytoplasm and round nuclei, frequently around epithelial component
    • Calcifications, multinucleated giant cells, foamy or hemosiderin laden macrophages and focal chronic inflammation
  • Epithelium:
    • Cells lining cysts
    • Mostly arranged in single layer with various morphology: flat, cuboidal, hobnail, clear cell
    • Rarely, foci of blunt and delicate papillae or foci of multiple layers of epithelium
  • Minimal cytologic atypia
  • Rare necrosis, no mitosis
Microscopic (histologic) images

Contributed by Bonnie Choy, M.D.
Multicystic tumor

Multicystic tumor

Flat and hobnail epithelium

Flat and hobnail epithelium

Hobnail epithelium

Hobnail epithelium

Cuboidal epithelium

Cuboidal epithelium


Stroma with variable cellularity

Stroma with variable cellularity

ER

ER

PR

PR

PAX8

PAX8

Virtual slides

Images hosted on other servers:

Cystic nephroma

Cytology description
Cytology images

Images hosted on other servers:

FNA

Molecular / cytogenetics description
  • Similar mRNA expression profile between adult cystic nephroma and MEST supports these tumors to represent opposite ends of same disease spectrum (Am J Surg Pathol 2009;33:72)
    • Highest differentially expressed gene: insulin-like growth factor 2
    • Lowest differentially expressed gene: carbonic anhydrase II
  • No DICER1 mutations as seen in pediatric cystic nephroma (Am J Surg Pathol 2017;41:472)
Sample pathology report
  • Left kidney, mass, partial nephrectomy:
    • Adult cystic nephroma, measuring 6.5 cm in greatest dimension (see comment)
    • Surgical margins, negative for tumor
    • Comment: The sections show a well circumscribed tumor composed of multiple cysts lined by flattened or cuboidal epithelium. Immunohistochemistry was performed to show the septal stroma is positive for ER and PR. The morphologic and immunohistochemical findings support the diagnosis of adult cystic nephroma.
Differential diagnosis
Board review style question #1
PR

A 6 cm predominantly well circumscribed, multicystic mass was incidentally found in a 55 year old woman. Sections of the partial nephrectomy showed the above histologic features. The stromal component is positive for ER and PR (shown above). What is the likely diagnosis?

  1. Adult cystic nephroma
  2. Angiomyolipoma with epithelial cysts
  3. Cystic partially differentiated nephroblastoma
  4. Multilocular cystic neoplasm of low malignant potential
Board review style answer #1
A. Adult cystic nephroma. Adult cystic nephroma is a well circumscribed, predominantly cystic mass. Angiomyolipoma with epithelial cysts shares overlapping histologic features but the stroma is immunopositive for melanocytic markers. Cystic partially differentiated nephroblastoma typically occurs in children. Multilocular cystic neoplasm of low malignant potential has nests of tumor cells with abundant clear cytoplasm and small nuclei without prominent nucleoli. None of the above choices, except for adult cystic nephroma, demonstrate immunoreactivity for ER and PR.

Comment Here

Reference: Adult cystic nephroma
Board review style question #2

Which of the following is true about adult cystic nephroma?

  1. Frequent DICER1 gene mutations
  2. Most are bilateral tumors
  3. Often indolent with very rare malignant transformation
  4. Typically occur in children with strong male predominance
Board review style answer #2
C. Often indolent with very rare malignant transformation. Adult cystic nephroma is considered benign with very rare reports of local recurrence or malignant transformation. The tumors usually present as unilateral tumors and typically seen in adult women. Unlike pediatric cystic nephroma, neither adult cystic nephroma nor mixed epithelial and stromal tumor has been found to have DICER1 mutations.

Comment Here

Reference: Adult cystic nephroma
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