Kidney tumor
Adult renal cell carcinoma
Unclassified renal cell carcinoma

Author: Nicole K. Andeen, M.D.
Senior Author: Maria Tretiakova, M.D., Ph.D.

Revised: 29 August 2018, last major update August 2018

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

PubMed Search: Unclassified renal cell carcinoma AND kidney AND (free full text[sb])

Cite this page: Andeen, N.K. Unclassified renal cell carcinoma. PathologyOutlines.com website. http://www.pathologyoutlines.com/topic/kidneytumormalignantnos.html. Accessed September 25th, 2018.
Definition / general
Essential features
  • Heterogeneous group of tumors, not readily classifiable
  • Molecular techniques may aid in classification
  • Important category enabling separation of unusual tumors from common subtypes and their further grouping / reclassification as distinct entities using advanced techniques or after gaining more data and experience
Sites
  • Kidney
Clinical features
Radiology description
  • Radiographic features similar to other RCCs
Prognostic factors
  • Outcome is often associated with grade, stage and clinicopathologic features known to be relevant in other forms of RCC (BJU Int 2012;110:786)
  • Most studies show that unclassified RCC are more aggressive than conventional RCC with 1.6 - 1.7 x the mortality of clear cell RCC in multivariate analysis (J Urol 2002;168:950, BJU Int 2007;100:802, BJU Int 2012;110:786), however one study showed that overall cancer specific survival is similar in matched cohorts after adjusting for grade, stage and other parameters (Urology 2010;76:580)
    • Despite that discrepancy > 50% of high grade unclassified RCC are dead of disease within 2 years
    • For low grade tumors a few anecdotal reports show indolent course
Case reports
Treatment
  • No standardized treatment but whenever feasible immunotherapy with nephrectomy is warranted (J Urol 2002;168:950)
Gross description
Gross images

Images hosted on PathOut server:

Contributed by Nicole K. Andeen, M.D. and Maria Tretiakova, M.D., Ph.D.

Unclassified RCC

Microscopic (histologic) description
Microscopic (histologic) images

Images hosted on PathOut server:

Contributed by Nicole K. Andeen, M.D. and Maria Tretiakova, M.D., Ph.D.

Unclassified RCC CDC like 10x

Unclassified RCC 20x

Unclassified RCC 20x - ChRCC

Unclassified 20x HLRCC like - CCRCC

Unclassified 20x Translocation - CCRCC


Images hosted on other servers:

Case report above - Various images

Positive stains
  • PAX8, PAX2
  • Staining patterns characteristic of a specific type of RCC preclude the diagnosis of unclassified RCC
Molecular / cytogenetics description
  • A study of 62 high grade unclassified RCCs revealed mutations in NF2 (18%), SETD2 (18%), BAP1 (13%), KMT2C (10%) and MTOR (8%) (Nat Commun 2016;7:13131)
  • Chromosome genomic array testing (array CGH) and SNP arrays are both useful tools in resolving 80 - 94% of unclassified RCCs with ~50% cases reclassified as clear cell RCC
  • Reclassified tumors show characteristic cytogenetic changes of certain subtype plus numerous additional copy number aberrations (Am J Surg Pathol 2009;33:1276)
Differential diagnosis
Board review question #1
    Which of the following is true about unclassified RCC?

  1. Any degree of staining for an immunohistochemical marker of interest (including TFE3, 2SC, CAIX) can establish the underlying diagnosis
  2. Areas with classic morphologic and immunophenotypic features of clear cell RCC or chromophobe RCC indicate the likely underlying etiology
  3. Unclassified RCC is a specific morphologic diagnosis
  4. Unclassified RCC is always high grade
Board review answer #1
B. Areas with classic morphologic and immunophenotypic features of clear cell RCC or chromophobe RCC indicate the likely underlying etiology
Board review question #2

    A tumor with marked morphologic heterogeneity including that seen in the image is best classified as:

  1. Chromophobe RCC
  2. Clear cell RCC
  3. MiT family RCC
  4. Papillary type 2 RCC
  5. Unclassified RCC
Board review answer #2
E. Unclassified RCC

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