Pediatric kidney tumours

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This article cover pediatric kidney tumours. Adult kidney tumour are covered in kidney tumours article. An introduction to pediatric pathology is in the pediatric pathology article.

Overview

These are diagnoses pediatric pathologists make.

The most common ones are:

  1. Wilms tumour.
  2. Clear cell sarcoma of the kidney.

Other renal tumours (not covered in this article):

The translocation carcinomas are covered in the kidney tumours article

Specific tumours

Wilms tumour

  • AKA nephroblastoma, AKA Wilms' tumour.

General

Gross

  • Lobulated tan mass.

Image: Wilms tumour (med.utah.edu).

Microscopic

Features - classically three components (blastema, immature stroma, tubules):[5]

  1. Malignant small round blue cells ("blastema"):
    • Size = ~ 2x RBC diameter.
    • Nuclear pleomorphism (variation of size, shape and staining).
      • Irregular nuclear membrane - important.
    • Scant/difficult to discern cytoplasm - basophilic (light blue).
    • Mitoses - common.
  2. Stroma ("immature stroma"):
    • Spindle cells:
      • Elliptical nuclear membrane.
      • Abundant loose cytoplasm.
  3. Tubular structures ("tubules"):
    • Usually clustered.
    • Vaguely resemble a glomerulus.
    • Usu. have a central (clear/white) space surrounded by a rim of intensely eosinophilic cytoplasm.
    • Nuclei of tubular structures often elongated and palisaded.

Other findings:

  • Commonly seen in association with nephrogenic rests.
    • Cluster of cells small (blue) cells; lack nuclear atypia seen in Wilms tumour.[6]
  • +/-Heterologous elements (skeletal muscle, smooth muscle adipose tissue, cartilage).[7]
    • Heterologous = doesn't normally belong there.[8]

DDx:

  • Metanephric adenoma.
  • Nephrogenic nests.
  • Other small round cell tumours.
  • Synovial sarcoma - esp. in adults.

Notes:

  • Palisade = fence made of stakes driven into the ground.[9]
  • Approximately 30-40% Wilms tumour cases have nephrogenic rests.[10]
  • The three phases are also called blastemal, epithelial and stromal.[7]

Images:

Anaplasia

Subclassified as:[7]

  1. Focal anaplasia.
  2. Diffuse anaplasia.

Criteria (all of the following):[7]

  1. Atypical mitoses.
  2. Nuclear hyperchromasia.
  3. Nuclear size variation (of the tumour cells) > 3x.

IHC

  • WT-1 +ve.

Metanephric stromal tumour

  • Abbreviated MST.

General

Gross

Features:[11]

  • Usu. renal medulla.
  • Solid or cystic.

Microscopic

Features:[11]

  • "Collarettes" - tumour cells surround blood vessels or renal tubules.
  • Spindle cells/stellate cells.
  • Variable cellular density - imparts a nodular appearance at low power.
  • Indistinct cell borders/cytoplasm.
  • Induces epithelioid morphology in smooth muscle cells.

Notes:

  • +/-Heterologous elements.

DDx:

Images:

Metanephric adenofibroma

General

  • Adults and children.

Microsopic

Features:[11]

Mesoblastic nephroma

General

  • Almost exclusively in infants.

Subclassified:

  1. Classic.
  2. Cellular.
  3. Mixed.

Gross

  • Renal sinus infiltration - common.

Microscopic

Classic

Features:[13]

  • Spindle cells in fascicles.
  • Infiltrative border.

Cellular

Features:[13]

  • Plump cells with vesicular nuclei.
  • Well-defined border.
  • Mitotically active.

Mixed

  • Like the name implies - both classic pattern and cellular pattern areas are present.[13]

Molecular

Cellular mesoblastic nephroma:

Clear cell sarcoma of the kidney

General

  • Common pediatric renal tumour - second only to Wilms tumour.
  • Aggressive.

Gross

  • Renal medulla.
  • +/-Cystic.

Microscopic

Features:[13]

  • Polygonal cells/Stellate cells.
  • Indistinct cell borders/cytoplasm; clear background.
  • No nucleoli.

Renal rhabdoid tumour

  • AKA rhabdoid tumour of the kidney, abbreviated RTK.

General

Microscopic

Features:[14][13]

  • Variable architecture.
  • Round cells.
  • Abundant cytoplasm with eosinophilic inclusions.
  • Eccentric vesicular nucleus.
  • Prominent nucleolus -- key feature.

Images:

IHC

  • INI1 -ve.

Renal cell carcinoma

General

  • Similar to in adults.
  • Clear cell RCC not common - a tumour with the clear cell histomorphology is more often a renal tumour with a Xp11.2 translocation.

Papillary RCC

See: (adult) renal cell carcinoma.
  • Most common form of RCC in children.

Clear cell RCC

See: (adult) renal cell carcinoma.

See also

References

  1. URL: http://emedicine.medscape.com/article/989398-overview. Accessed on: 9 March 2011.
  2. Online 'Mendelian Inheritance in Man' (OMIM) 194072
  3. Online 'Mendelian Inheritance in Man' (OMIM) 130650
  4. Online 'Mendelian Inheritance in Man' (OMIM) 194080
  5. Mitchell, Richard; Kumar, Vinay; Fausto, Nelson; Abbas, Abul K.; Aster, Jon (2011). Pocket Companion to Robbins & Cotran Pathologic Basis of Disease (8th ed.). Elsevier Saunders. pp. 254-5. ISBN 978-1416054542.
  6. URL: http://www.pathconsultddx.com/pathCon/diagnosis?pii=S1559-8675%2806%2970416-8. Accessed on: 28 March 2011.
  7. 7.0 7.1 7.2 7.3 Humphrey, Peter A; Dehner, Louis P; Pfeifer, John D (2008). The Washington Manual of Surgical Pathology (1st ed.). Lippincott Williams & Wilkins. pp. 282. ISBN 978-0781765275.
  8. URL: http://www.biology-online.org/dictionary/Heterologous. Accessed on: 1 October 2011.
  9. URL: http://www.thefreedictionary.com/palisaded. Accessed on: 2 February 2011.
  10. Coppes MJ, Haber DA, Grundy PE (September 1994). "Genetic events in the development of Wilms' tumor". N. Engl. J. Med. 331 (9): 586–90. doi:10.1056/NEJM199409013310906. PMID 8047084.
  11. 11.0 11.1 11.2 11.3 Humphrey, Peter A; Dehner, Louis P; Pfeifer, John D (2008). The Washington Manual of Surgical Pathology (1st ed.). Lippincott Williams & Wilkins. pp. 283. ISBN 978-0781765275.
  12. 12.0 12.1 Palese, MA.; Ferrer, F.; Perlman, E.; Gearhart, JP. (Sep 2001). "Metanephric stromal tumor: a rare benign pediatric renal mass.". Urology 58 (3): 462. PMID 11549506.
  13. 13.0 13.1 13.2 13.3 13.4 13.5 Humphrey, Peter A; Dehner, Louis P; Pfeifer, John D (2008). The Washington Manual of Surgical Pathology (1st ed.). Lippincott Williams & Wilkins. pp. 284. ISBN 978-0781765275.
  14. Humphrey, Peter A; Dehner, Louis P; Pfeifer, John D (2008). The Washington Manual of Surgical Pathology (1st ed.). Lippincott Williams & Wilkins. pp. 627. ISBN 978-0781765275.