Pseudocarcinomatous Hyperplasia of the Urinary Bladder

Abstract

We review the morphology and differential diagnoses of pseudocarcinomatous hyperplasia of the bladder, using a study case to illustrate the discussion. Pseudocarcinomatous hyperplasia is a rare, reactive response to an ischemic insult, classically to radiation therapy, and consists of proliferative, pseudoinfiltrative urothelial nests within the stroma. The presence of background radiation therapyrelated changes, such as numerous dilated thrombosed vessels, reactive-appearing endothelial and stromal cells, edema, and hemorrhage, can provide clues to the diagnosis. The main differential diagnoses include invasive urothelial carcinoma and the nested variant of urothelial carcinoma; morphologic features, such as the presence or absence of background therapy-related changes and the architecture and the cytologic atypia of the nests, can help distinguish between pseudocarcinomatous hyperplasia and urothelial carcinoma.

Iatrogenic changes in the urinary tract

“…Similar data come from p16 immunohistochemistry. These results need further AMACR and p16 validation studies …”

“…Less significant abnormalities may be seen in the deeper layers of the urothelium (Figure , Table ). Limited data suggest that immunohistochemical expressions of p53, CD44, CK20 and AMACR (negative expression) are similar to that seen in reactive urothelium …”

Pseudocarcinomatous hyperplasia associated with primary lymphoma in the urinary bladder: a case report

“…Pseudocarcinomatous hyperplasia is a reactive process in which proliferative benign urothelial nests involve the subepithelial connective tissue [1][2][3]. Pathologists must be cognizant of this entity because these urothelial nests can be quite extensive and mimic an invasive urothelial carcinoma (UC), including its nested variant, as in our current case.…”

“…These nests can be quite proliferative and back to back [1]; in 1 series by Chan and Epstein [11], 45% of cases showed "marked" proliferations, meaning they occupied more than 50% of the subepithelial connective tissue. These nests can range from being bland to having nuclear atypia; often, the associated atypia is random, degenerative atypia commonly seen after radiation therapy.…”

“…The overlying urothelium may have random, degenerative-type atypia with "smudged" chromatin, nuclear or cytoplasmic vacuoles, or cytoplasmic ballooning; usually, even those cells with nuclear atypia and enlargement still have abundant cytoplasm. Overlying papillary neoplasia or flat UC in situ should be absent [1]. Follow-up in various case series (average follow-up times ranging from 9 to 27 months) has shown that nearly all of the patients have had a benign course with no subsequent development of UC [2,3,11,12].…”