Xanthogranulomatous pyelonephritis

Xanthogranulomatous pyelonephritis, abbreviated XGP, is an inflammatory process of the kidney that can mimic renal cell carcinoma.

General

• May mimic renal cell carcinoma - especially radiologically.
• Usually lower pole.^{[citation needed]}
• Associated with:
  • Diabetes mellitus.
  • History of UTI.
  • Nephrolithiasis.
  • GU obstruction.
• Occasionally an indication of nephrectomy.
• Most common organism (in the context of nephrectomy specimens) - Proteus mirabilis.

Microscopic

• Abundant macrophages.
• +/-Giant cells.

DDx:

• Malakoplakia.
  • Basophilic inclusions -- inside or outside of macrophages - often size of RBC or larger (Michaelis-Gutmann bodies).
• RCC - especially PRCC (as this has foamy macrophages).
• Granulomatous disease.
• Chronic pyelonephritis.
• Interstitial nephritis.

Image

• 

  Xanthogranulomatous pyelonephritis - CD68 stain. (WC/Nephron)

Stains

• PAS-D -ve.
  • Done to look for malakoplakia.

IHC

• CD68 +ve.
• RCC markers (CD10, RCC) all negative.

Sign out

RIGHT KIDNEY, NEPHRECTOMY:
- XANTHOGRANULOMATOUS PYELONEPHRITIS.
- CHRONIC INTERSTITIAL NEPHRITIS.
- INCREASED NUMBERS OF TOTALLY SCLEROSED GLOMERULI AND GLOMERULI WITH FOCAL 
  SEGMENTAL GLOMERULOSCLEROSIS.
- MARKED INTERSTITIAL FIBROSIS.
- NEGATIVE FOR MALIGNANCY.

COMMENT:
Immunostaining demonstrates abundant CD68 positive cells (macrophages).  A CD10 immunostain 
is non-concerning (it highlights glomeruli). A pankeratin immunostain is non-concerning 
(it highlights benign renal tubules).

Compatible XGP

"KIDNEY" LESION, LEFT, BIOPSY:
- FIBROMUSCULAR TISSUE WITH A MIXED INFLAMMATORY INFILTRATE.
- CELLULAR DEBRIS WITH SURROUNDING LOOSELY AGGREGATED HISTIOCYTES.
- NO RENAL PARENCHYMA IDENTIFIED.
- NEGATIVE FOR MALIGNANCY.

COMMENT:
A SMA immunostain highlights the muscle component, and a CD68 immunostain marks 
abundant histiocytes. No epithelial component is identified with a pankeratin 
immunostain. 

See also

• Kidney tumours.