Kidney tumor

Benign adult tumors

Metanephric adenoma

Editor-in-Chief: Debra L. Zynger, M.D.
Tatjana Antic, M.D.

Last author update: 31 March 2020
Last staff update: 28 November 2022 (update in progress)

Copyright: 2003-2022,, Inc.

PubMed Search: Metanephric adenoma [title] pathology loattrfree full text[sb]

Tatjana Antic, M.D.
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Cite this page: Antic T. Metanephric adenoma. website. Accessed December 9th, 2022.
Definition / general
  • Member of metanephric tumor family, including metanephric adenofibroma and metanephric stromal tumor
Essential features
  • Benign tumor composed of cytologically bland embryonic looking epithelium with frequent psammomatous calcifications
  • It can be seen in patients from pediatric to old adult age
  • Metanephroid renal tumor, nephroblastoma-like adenoma, nephrogenic nephroma
ICD coding
  • ICD-O: 8325/0 - metanephric adenoma
  • An uncommon, usually asymptomatic, incidentally discovered renal neoplasm
  • Rare, less than 0.5% of all renal neoplasm
  • Age range 5 - 84 years (mean about 54) (Oncotarget 2016;8:54096)
  • 60% are female
  • Renal cortex
Clinical features
  • Usually discovered incidentally with no presenting symptoms
  • If presenting with symptoms, can demonstrate hematuria, pyrexia, flank pain, abdominal mass and polycythemia (Oncol Lett 2016;11:352)
  • Diagnosed by histopathologic examination of excised tissue
  • If diagnosis is questionable, immunohistochemistry can differentiate metanephric adenoma from its mimics
  • Routine laboratory within normal limits in incidental cases
  • Polycythemia might be suggestive of renal tumor
Radiology description
Radiology images

Images hosted on other servers:

CT scan

Prognostic factors
Case reports
  • Surgical resection is a curative
Gross description
  • Most are 3 - 6 cm in diameter although 15 cm tumor has been reported (Urology 2017;101:147)
  • Mostly unilateral and unifocal
  • Rare cases with cystic change (Urology 2017;101:147)
  • Circumscribed, not encapsulated with pushing border
  • Cut surface is tan to grey and can be soft or firm and occasionally hemorrhage and necrosis can be present in larger tumors
  • Calcifications are often seen grossly
Gross images

Contributed by Debra L. Zynger, M.D.

Partial nephrectomy

Radical nephrectomy

Microscopic (histologic) description
  • Classic appearance is a cellular blue tumor composed of tightly packed tubules, long branching and angulated ducts and abortive glomeruli
  • Tumor cells have scant cytoplasm and nuclei are small with no nucleoli
  • Mitotic figures are very rare or absent
  • Stroma is scant and it can be edematous and occasionally look scar-like
  • Psammomatous calcifications can be abundant (Oncol Lett 2015;10:1816)
Microscopic (histologic) images

Contributed by Tatjana Antic, M.D.

Well circumscribed



Packed tubules

Loose stroma

Mitotic figure


Pseudopapillary and glomeruloid



Virtual slides

Images hosted on other servers:

Metanephric adenoma

Cytology description
Positive stains
Electron microscopy description
Molecular / cytogenetics description
Sample pathology report
  • Right kidney, partial nephrectomy:
    • Metanephric adenoma, 3.5 cm in greatest dimension (see comment)
    • Surgical margins, negative for tumor
    • Comment: The sections show well circumscribed tumor composed of tightly packed tubules. The nuclei are small and devoid of nucleoli. No mitotic activity or necrosis is present. The cytoplasm is scant. Numerous psammomatous calcifications are present. Immunohistochemical stains for WT1 and BRAF are positive.
Differential diagnosis
Board review style question #1

    A 66 year old woman with flank pain is found to have polycythemia. The computer tomography study shows a 3.8 cm solid, circumscribed and hypovascular renal cortical tumor. Which renal tumor is likely to be associated with the above clinical presentation, imaging study and histomorphology?

  1. Angiomyolipoma, triphasic
  2. Clear cell renal cell carcinoma
  3. Metanephric adenoma
  4. Nephroblastoma
  5. Urothelial carcinoma
Board review style answer #1
C. Metanephric adenoma. Metanephric adenoma is associated with polycythemia and a hypovascular renal mass on imaging study. The section shows a well circumscribed renal tumor composed of tightly packed tubules. Angiomyolipoma contain adipose tissue which is easily seen on CT scan. Patient age argues against diagnosis of nephroblastoma. Urothelial carcinoma is neither cortical tumor nor it is circumscribed. Clear cell renal cell carcinoma is hypervascular tumor although it can cause polycythemia and is not basophilic.

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Reference: Metanephric adenoma
Board review style question #2

    A renal mass from a 43 year old woman shows a tumor composed of tightly packed basophilic tubules. The cell nuclei are cytologically bland and cytoplasm is scant. Numerous psammomatous calcifications are present. No mitotic activity or necrosis is present. Which is the immunohistochemical profile that should be seen in this tumor?

  1. PAX8+, WT1+, CK7-, CD57+, BRAF+
  2. PAX8-, WT1+, CK7-, CD57+, BRAF-
  3. PAX8+, WT1+, CK7-, CD57+, BRAF-
  4. PAX8+, WT1-, CK7-, CD57+, BRAF+
  5. PAX8+,WT1-, CK7+, CD57+, BRAF+
Board review style answer #2
A. PAX8+, WT1+, CK7-, CD57+, BRAF+. This is a metanephric adenoma. The differential diagnoses include papillary renal cell carcinoma, type 1, solid variant and adult epithelial predominant nephroblastoma. Papillary renal cell carcinoma, type 1 is a PAX8+, vimentin+, CK7+, AMACR+, WT1-, CD57-, BRAF- tumor as opposed to metanephric adenoma that is positive for WT1, CD57 and BRAF and negative for CK7. Adult nephroblastoma is positive for WT1 but negative for CD57 and BRAF.

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Reference: Metanephric adenoma
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