DNA profile of nephrogenic adenoma assessed by flow cytometry

Nephrogenic Adenoma of the Urinary Tract

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.

Hepatocyte nuclear factor-1β expression in clear cell adenocarcinomas of the bladder and urethra: diagnostic utility and implications for histogenesis

The histogenesis of clear cell adenocarcinoma of the bladder/urethra is uncertain. Hepatocyte nuclear factor-1β is a homeodomain protein that has been reported to be frequently overexpressed in ovarian clear cell adenocarcinoma in comparison with rare or no expression in other types of epithelial ovarian tumors. We assessed the expression of hepatocyte nuclear factor-1β in a series of 18 clear cell adenocarcinomas of the bladder and urethra and compared it with that of invasive high-grade transitional/urothelial carcinoma (n = 35); adenocarcinomas of the bladder, urethra, and paraurethral glands (n = 21); as well as nephrogenic adenomas of the bladder (n = 8). Staining intensity and extent were evaluated using a 4-tiered grading system (0-3). A case was considered positive for hepatocyte nuclear factor-1β if 10% or more of tumor cells showed at least weak nuclear staining or if any moderate or strong nuclear staining was observed. All 18 clear cell adenocarcinomas exhibited nuclear staining in at least 50% of tumor cells (16 strong, 1 moderate, and 1 weak with focal strong nuclear staining) in comparison with positive nuclear staining (moderate) in 1 of 21 bladder adenocarcinoma, 1 of 35 invasive high-grade transitional/urothelial carcinoma (weak to moderate staining), and 2 of 8 nephrogenic adenomas (1 weak and 1 moderate to strong staining). We concluded that hepatocyte nuclear factor-1β is a useful marker in differentiating clear cell adenocarcinomas of the bladder/urethra from invasive high-grade transitional/urothelial carcinoma and other types of bladder adenocarcinomas and to a lesser extent from nephrogenic adenomas. Hepatocyte nuclear factor-1β is of no diagnostic utility in discriminating primary bladder/urethral clear cell adenocarcinomas from metastatic clear cell adenocarcinomas of the female genital tract to the bladder/urethra. From a histogenesis standpoint, although the expression of hepatocyte nuclear factor-1β in both gynecologic and urologic tract clear cell adenocarcinomas may point to a Müllerian derivation/differentiation, this immunohistochemical evidence is insufficient to completely exclude an urothelial association.

Expression of PAX8 in nephrogenic adenoma and clear cell adenocarcinoma of the lower urinary tract: evidence of related histogenesis?

Recent evidence has showed that nephrogenic adenoma is a true "nephrogenic" lesion derived from the proliferation of exfoliated and implanted renal tubular cells in the urinary tract, a process that closely resembles the formation of endometriosis. This new concept has led to the identification of renal transcription factor PAX2 as a diagnostic marker for nephrogenic adenoma. PAX8 is another transcription factor structurally and functionally related to PAX2. Both are cell lineage restricted transcription factors expressed in normal and neoplastic tissues of related origin, including renal tubular cells in both fetal and adult kidneys. In this study, we investigated the expression of PAX8 in nephrogenic adenoma and its mimics. We report here that PAX8 was detected in all nephrogenic adenomas (N=35) and clear cell adenocarcinoma of the lower urinary tract (N=7), but not in prostate adenocarcinoma (N=100), adenocarcinoma (N=9), squamous cell carcinoma (N=5), or urothelial carcinoma (N=48) of the urinary bladder and its variants. PAX8 was neither detected in normal urothelium of the urinary bladder nor in prostate glands and stroma. PAX2 was also detected in 2 of the 7 clear cell adenocarcinomas of the lower urinary tract. We suggest that PAX8 is an additional marker for identifying nephrogenic adenoma. Expression of PAX8 or PAX2 in both nephrogenic adenoma and clear cell adenocarcinoma of the lower urinary tract may indicate a possible related tissue origin for these 2 lesions; both may be derived from proliferating renal tubular cells in the urinary tract. In addition, detection of PAX8 or PAX2 in clear cell adenocarcinoma of the lower urinary tract is helpful in differentiating it from urothelial carcinoma and its variants and adenocarcinomas of the urinary bladder or of the prostate.

Nephrogenic adenoma: an update on an innocuous but troublesome entity

Nephrogenic adenoma (NA) is a rare benign lesion of the urothelial tract that is typically preceded by some form of genitourinary insult. The pathogenesis of NA is not entirely clear. Although generally presumed to be a metaplastic process of the urothelium, recent evidence suggests that NA may in fact be derived from detached renal tubular cells implanting along the urothelial tract in previously injured areas, at least in cases associated with a kidney transplant. On light microscopy, NA shows a variety of patterns, including tubulocystic, papillary, and much less frequently solid, that often coexist. Recognition of its characteristic patterns, and awareness of its unusual architectural and cytologic features, is key to making the diagnosis of NA and distinguishing this lesion from malignant neoplasms occurring at the same sites, in particular, clear cell carcinoma, nested or microcystic variants of urothelial carcinoma and prostatic adenocarcinoma. Although straightforward in most cases, the correct diagnosis may be difficult to make on limited tissue samples. A number of immunohistochemical markers have been studied in an attempt to characterize NA; however, to date there is no specific immunohistochemical profile to distinguish this lesion from its malignant mimickers, although PAX2, a new marker, may prove to be helpful in this regard. Clinicopathologic correlation with careful attention to morphology remains the pillar in establishing the correct diagnosis.

Nephrogenic Adenoma: Immunohistochemical Evaluation for Its Etiology and Differentiation From Prostatic Adenocarcinoma

Context.—Nephrogenic adenoma is a rare benign lesion of the urinary tract. Owing to its strong association with a history of urinary tract irritation, nephrogenic adenoma was initially thought to originate from urothelial metaplasia; however, no solid proof of this association has been found. More recent investigation has pointed to a renal tubular cause. In addition to its uncertain origin, there can be diagnostic difficulty in distinguishing nephrogenic adenoma from prostatic carcinoma, particularly when dealing with lesions from the prostatic urethra.

Objective.—To elucidate a possible histogenic relationship between nephrogenic adenoma and renal tubules, and also to evaluate the role of immunohistochemistry in the diagnostic distinction between nephrogenic adenoma and prostate carcinoma.

Design.—Immunohistochemical studies were performed for P504S, prostate-specific antigen, CD10, p63, and epithelial membrane antigen on 9 cases of nephrogenic adenoma, 10 cases of normal renal parenchyma, and 10 cases of prostatic tissue, both benign and malignant.

Results.—Nephrogenic adenoma shares the same immunohistochemical profile as distal renal tubules: both are positive for P504S and epithelial membrane antigen and negative for p63, CD10, and prostate-specific antigen. Prostatic adenocarcinoma tissue was positive for P504S and prostate-specific antigen, and normal prostatic gland tissue was positive for prostate-specific antigen and negative for P504S; p63-stained basal cells in normal prostatic gland tissue but did not react with prostatic adenocarcinoma tissue. The CD10 inconsistently stained normal and neoplastic prostatic gland tissue. Epithelial membrane antigen stain was negative in prostatic carcinoma, with rare occasional reactivity in normal prostatic glands.

Conclusion.—These findings provide supporting evidence that nephrogenic adenoma is derived from distal renal tubules. Our results also demonstrated that the combination of P504S and prostate-specific antigen with epithelial membrane antigen is a valuable tool in distinguishing prostatic carcinoma from nephrogenic adenoma.

DNA profiles and numeric histogram classifiers in nephrogenic adenoma

BACKGROUND

The malignant potential of nephrogenic adenoma is still a matter of controversy and therapeutic regimens of this morphologic entity range from partial, even total cystectomy to watchful waiting. The objective of the current study was to evaluate several robust image cytometry-DNA histogram classifiers and to search among those for factors that separate a biologically nonaggressive metaplastic lesion from lesions with increased malignant potential.

METHODS

The study included bladder irrigation specimens, 23 preceding transurethral resection of nephrogenic adenoma and 24 preceding resection of papillary bladder carcinoma. Feulgen-stained nuclei were imported to a static image analysis system, and densitometric data were interpreted by two different software programs. Histograms were described numerically by DNA index, 2c deviation index, and by 5c/9c-exceeding and euploid polyploidy rates. In addition, an interpretation algorithm based on a dual parameter analysis with an integrated automatic threshold was used.

RESULTS

The numeric classification of DNA histograms of patients suffering from nephrogenic adenoma resulted in DNA indices between 0.91 and 1.15. The 2c deviation indices ranged from 0.03 to 0.43, and the 5c exceeding rates ranged from 0.0 to 1.58. None of the measurements showed nuclei exceeding 9c. The p25-75 ranges of 2c deviation indices in nephrogenic adenoma and papillary urothelial carcinoma did not overlap. These findings might be explained by minor proliferative activity in nephrogenic adenoma. Euploid polyploidy rates less than 5% confirm this explanation. Risk analysis documented high risk only for those patients with nephrogenic adenomas who had proven transitional cell carcinoma in their history.

CONCLUSIONS

DNA estimation by image cytometry of urinary bladder irrigation specimens appears able to separate papillary bladder lesions. The method detects those lesions with higher malignant potential but is limited in separating entities with low malignant potential. Comparison of the discriminative power of robust numeric DNA classifiers reveals the 2c deviation index superior to the widely used DNA index and the 5c exceeding rate in this material.

Atypical nephrogenic metaplasia of the urinary tract: a precursor lesion?

BACKGROUND

Nephrogenic metaplasia with cytologic atypia (atypical nephrogenic metaplasia) is occasionally encountered and its biologic potential is uncertain.

METHODS

The authors describe 18 cases of atypical nephrogenic metaplasia characterized by the presence of prominent cytologic atypia, including nuclear enlargement, nuclear hyperchromasia, and enlarged nucleoli. DNA ploidy analysis by digital image analysis and immunostaining for high-molecular-weight cytokeratin (34betaE12), cytokeratin 7, cytokeratin 20, carcinoembryonic antigen (CEA), epithelial membrane antigen (EMA), p53, and MIB-1 were performed in 9 cases.

RESULTS

The mean patient age was 62 years (median, 65 years; range, 39-84 years). The male-to-female ratio was 2.6:1. Two patients had a history of noninvasive papillary urothelial carcinoma. The typical clinical presentation was hematuria (8 patients) and voiding symptoms (5 patients). Cystoscopic findings were suspicious for neoplasm in 7 of 13 cases. The neoplastic cells were positive for high-molecular-weight cytokeratin, cytokeratin 7, and EMA, and were usually negative for cytokeratin 20 and CEA. p53 nuclear accumulation and increased MIB-1 labeling index were seen in 4 cases. DNA ploidy analysis showed aneuploid pattern in 2 of 9 cases. The mean patient follow-up was 3.5 years (range, 0.5-10.6 years); 2 patients had recurrent nephrogenic metaplasia, and the remainder were alive without recurrence or urothelial carcinoma.

CONCLUSIONS

Atypical nephrogenic metaplasia is benign; it occasionally displays substantial cytologic abnormalities of no apparent clinical significance. Awareness of the spectrum of cytologic changes within this entity is critical to prevent overdiagnosis of cancer and avoid unnecessary treatment. There is no direct evidence that links atypical nephrogenic metaplasia to cancer.

Nephrogenic adenoma in renal transplant recipients: a truly benign lesion?

OBJECTIVES

Nephrogenic adenoma is a benign metaplastic lesion of the urinary bladder, reported to occur as a response to inflammation, trauma, intravesical therapies, and after renal transplantation. The aim of this study was to evaluate on the basis of chromosomal analysis whether nephrogenic adenoma really is benign.

METHODS

Twelve renal transplant recipients with histologically verified nephrogenic adenoma were analyzed for numerical aberrations of chromosomes 7, 9, and 17. Results were related to total DNA content, p53 and Ki-67 positivity, and clinical outcome. Ten patients with superficial bladder cancer and 10 healthy renal transplant recipients formed the control groups.

RESULTS

All 12 patients with nephrogenic adenoma had monosomy 9 in a mean of 24.3% (range 20% to 30%) of the evaluated cells; 3 patients had an additional trisomy 7 in a mean of 8% (range 6% to 10%) of the counted cells. Chromosome 1 7 was disomic in all patients. DNA histograms were diploid in 11 of the 12 patients and aneuploid in 1 patient. No p53 and Ki-67 positivity was present in this group. All patients with superficial bladder cancer had monosomy 9 in a mean of 79.8% (range 75% to 85%) of the counted cells. Two patients were found to have an additional trisomy 7 in 50% and 65% of the cells, respectively. The latter had an aneuploid histogram; the others had haploid/diploid histograms. p53 was negative in all specimens. Ki-67 positivity was present in 70% of these patients. All healthy transplant recipients had disomic chromosomal patterns according to diploid DNA histograms and negative immunocytochemical results.

CONCLUSIONS

Even if in a lower percentage of cells, aberrations of chromosome 7 and 9 were detected in nephrogenic adenoma. It therefore cannot be excluded that nephrogenic adenomas in immunosuppressed renal transplant recipients may develop into malignant lesions.

Nephrogenic adenoma of the bladder in renal transplant recipients: a report of 9 cases with assessment of deoxyribonucleic acid ploidy and long-term followup

PURPOSE

We evaluated the outcome of nephrogenic adenoma, a benign tumor rarely encountered in renal transplant recipients.

MATERIALS AND METHODS

Between 1985 and 1993, 9 renal transplant recipients with a nephrogenic bladder adenoma removed by endoscopic resection were followed for 24 to 88 months (mean 40). Tumor deoxyribonucleic acid ploidy was assessed by flow cytometry at diagnosis and/or relapse.

RESULTS

The relapse rate was 88%. The tumors were diploid and of low proliferating potential, and showed no malignant transformation.

CONCLUSIONS

Our study confirms the lack of premalignant potential of nephrogenic adenomas. However, since transplant recipients might be at increased risk for bladder cancer, they should be followed closely.

Bladder washing flow cytometry assessment of nephrogenic adenoma of the bladder

A case of nephrogenic adenoma of the bladder is reported. This rare benign lesion that histologically resembles primitive renal collecting tubules is considered to represent a metaplastic response of urothelium to several stimulating factors. DNA flow cytometry performed on preoperative bladder washing revealed an aneuploid phenotype.