Nephrogenic adenoma (nephrogenic metaplasia)

Definition

A benign urogenital proliferation that may be found in the bladder, urethra, renal pelvis or ureters. It is thought to represent a reaction of the urothelium to injury2 by instrumentation, surgery or calculi. When the lesion develops in renal transplant recipients, the lesions are composed of donor cells, indicating that they probably represent implanted detached renal tubules3.

Epidemiology

This is an uncommon lesion of adults.

Macroscopic appearances

The lesions may be single or multiple.

Histopathology

Nephrogenic adenoma has a variable architecture; papillary, tubular, nested, hobnail or solid. The hobnails may line vessels-like structures. Small tubules may have a pseudoinfiltrative pattern. Dilated tubules filled with eosinophilic material produce a thyroidised appearance. A basal layer is lacking. There may be cytological atypia with focally prominent nucleoli, but mitoses are absent. The stroma may be oedematous or inflammatory. Calcification and ossification occur3.

Immunohistochemistry

 

 

various sites

bladder

prostate

 
 

P504S

22/383

3/161

4/41

 

PSA

 0/223

0/161

0/41, 1/112

PSAP

 

 

3/102

CK7

 

 

9/92

34bE12

10/263

4/161

1/41, 5/92

p63

 

0/161

0/41

       

Differential diagnosis

References

1Skinnider, B. F., E. Oliva, et al. (2004). "Expression of alpha-methylacyl-CoA racemase (P504S) in nephrogenic adenoma: a significant immunohistochemical pitfall compounding the differential diagnosis with prostatic adenocarcinoma." Am J Surg Pathol 28(6): 701-5.

2Allan, C. H. and J. I. Epstein (2001). "Nephrogenic adenoma of the prostatic urethra: a mimicker of prostate adenocarcinoma." Am J Surg Pathol 25(6): 802-8.

3Gupta, A., H. L. Wang, et al. (2004). "Expression of alpha-methylacyl-coenzyme A racemase in nephrogenic adenoma." Am J Surg Pathol 28(9): 1224-9.

This page last revised 1.11.2004.

©SMUHT/PW Bishop