Nephrogenic Adenoma of the Urinary Tract

Abstract

Nephrogenic adenoma (NA) is an uncommon and intriguing lesion in the urinary tract. The pathogenesis of NA is not entirely clear. NA was considered to be a metaplastic process of the urothelium in response to chronic irritation of the urinary tract. However, recent evidence has shown that NA is not a metaplastic lesion but rather a proliferation of exfoliated and implanted renal epithelial cells in the urinary tract. Histologically, NAs exhibit, singly or in combination, tubules, small papillae, and microcystic structures lined by cells with little cytological atypia and focal hobnail changes. Solid formations and compressed spindled cells within a fibromyxoid background are rarely observed. Differential diagnosis includes, but is not limited to, malignant neoplasms occurring at the same sites, in particular urothelial carcinoma with deceptively bland morphology (with small tubules, microcystic and nested variants), prostatic adenocarcinoma, and clear cell adenocarcinoma. Immunohistochemical studies with antibodies targeting members of the paired box gene family (PAX2 and/or PAX8) in NAs may be helpful in the differential diagnosis of urothelial lesions and prostatic adenocarcinoma. NAs are most likely to be confused with clear cell adenocarcinoma, especially in small biopsy specimens. This is confounded by both lesions being frequently positive for PAX2, PAX8, and CK7 and not infrequently positive for p504S (α-methylacyl-CoA-racemase, AMACR) by immunohistochemistry. Recognition of its characteristic morphological patterns and awareness of its unusual architectural and cytological features are important in making the diagnosis of NA and distinguishing this lesion from its mimickers.

Nephrogenic Adenomas in Pediatric Patients: A Morphologic and Immunohistochemical Study of 21 Cases

“…These immunohistochemical results are all in accordance with those previously reported in adult nephrogenic adenomas [13][14][15][16]. A study by Fromont and colleagues reported nonspecific positive staining for P504S and CDIO in nephrogenic adenomas as a result of the use of avidin-biotin detection procedure reacting with the high level of endogenous biotin [14].…”

Telomerase reverse transcriptase promoter mutations in glandular lesions of the urinary bladder

“…They are rarely a challenge for the experienced pathologist [8]. On the other hand, nephrogenic adenoma ( Figure B-D), a relatively uncommon lesion induced by chronic irritation of the urothelial mucosa, is a benign entity and a common mimic of adenocarcinoma [8,9]. We collected 5 cases each from von Brunn nests, cystitis glandularis, and cystitis cystica as well as 10 cases of nephrogenic adenoma.…”

Recurrence of childhood nephrogenic adenoma in urinary bladder developed four years after previous surgery despite intravesical sodium hyaluronate therapy

“…[3,9,11] Histopathological study is needed to distinguish it from malignancy. [12] NA generally demonstrates multiple histologic patterns, with a minority composing of small tubules or papillary projections alone. Small tubules are often surrounded by a thickened hyalinized basement membrane without any desmoplastic stromal response.…”

“…Small tubules are often surrounded by a thickened hyalinized basement membrane without any desmoplastic stromal response. [12,13] Treatment of intravesical lesions consists of TUR and fulguration and rarely partial or total cystectomy may be required after ineffective TUR. [3,14] In our case patient underwent open submucosal resection and fulguration.…”