Home > E. Pathology by systems > Urinary system > Urinary bladder > Brunn nest

Brunn nest

Wednesday 25 January 2012

islets of von Brunn; islet of von Brunn; Brunn’s nests

Digital slide

- Cystic islets of von Brunn : NCK8-184 (ICSFramework)

Digital case

- HPC:362 : Cystic islets of von Brunn

Brunn nests represent a commonly encountered reactive change and consist of solid nests of urothelial cells within the lamina propria. Some nests may retain connection with the overlying urothelium, where as others appear free in the lamina propria.

Some bladder specimens show exuberant Brunn nests which may mimic nested variant of urothelial carcinoma. Small solid clusters of urothelial cells lacking cytologic atypia scattered throughout the lamina propria can be seen. The nests stop just short of muscularis propria.

Differential diagnosis

- nested variant of urothelial carcinoma

  • The most important differential diagnosis is with nested variant of urothelial carcinoma.
  • Brunn nests are usually large, superficially located, regular in shape and spacing, and lack cytologic atypia.
  • The relatively uniform size and shape of the nests and the lack of cytologic atypia are seen.
  • Irregularity in size and shape, location deep within the lamina propria, and cytologic atypia should raise the concern for nested variant of urothelial carcinoma.

Anomalies

Brunn nests, cystitis cystica and cystitis glandularis are reactive urothelial changes commonly encountered in bladder specimens. Brunn nests are invaginations from the overlying urothelium into the lamina propria.

When Brunn nests become cystically dilated (with or without eosinophilic secretions in the lumen) - this change is referred to as cystitis cystica. When the urothelial cell nests show a central lumen lined by glandular epithelium, it is referred to as cystitis glandularis. Most areas of cystitis cystica and cystitis glandularis are microscopic.

In some cases, florid cystitis cystica and cystitis glandularis may form polypoid masses that clinically mimic urothelial neoplasia.