Urothelial carcinomas with small cystic spaces containing mucin or cell debris (Figure 1) and involvement of a von Brunn nest by urothelial carcinoma, which is not lined by columnar epithelium ("glandlike lumina"), should not be confused with adenocarcinoma.
The benign lesions include cystitis cystica, cystitis glandularis, von Brunn nests, nephrogenic adenoma, mesonephric remnant, intestinal metaplasia, and urachal remnant.
The main differential diagnosis is von Brunn nests. (27) In transurethral resection specimens, the first clue of nested urothelial carcinoma is the architectural arrangement of the epithelial nests.
Large nested variant of urothelial carcinoma: 23 cases mimicking von Brunn nests and inverted growth pattern of noninvasive papillary urothelial carcinoma.
Many of the specimens that appeared cystoscopically suggestive of CIS either due to erythema or irregularity of the surface mucosa, were found to have benign pathologic features (Figure 2, A through F) such as florid proliferation of von Brunn nests
or cystitis cystica et glandularis.
Florid von Brunn nests
mimicking urothelial carcinoma: a morphologic and immunohistochemical comparison to the nested variant of urothelial carcinoma.
Nested urothelial carcinoma is a specific variant of invasive urothelial carcinoma in which the invasive urothelial nests are deceptively cytologically bland and mimic von Brunn nests
(5); despite their bland cytologic features, nested urothelial carcinomas can often be deeply invasive.
von Brunn nests
are present in the normal urothelium and are thought to arise from invaginations of the urothelial mucosa into the underlying lamina propria.
Von Brunn nests
in lamina propria, including cystitis cystica (Figure 2, E and F; arrow), were similarly straight forward to identify.
* Cells in von Brunn nests
have slightly larger nuclei than overlying urothelial cells have.
Von Brunn Nests
.--Von Brunn nests
are aggregates of urothelial cells that represent invaginations from the surface urothelium.
Urine samples (x2, voided urine) showed few red blood cells and were reported as "no malignancy identified." The biopsy specimen showed BPEPs (PSA-positive glands) and foci of von Brunn nests