Nephrogenic adenoma--a study with special reference to clinical presentation

p16 Immunohistochemical Expression in Nephrogenic Adenoma

Nephrogenic adenoma (NA) is a rare metaplastic entity commonly associated with a prior urothelial injury. Most are seen in the urinary bladder and a minority involve the urethra. In this study, we evaluated the expression of p16 as a surrogate marker of this entity and correlated it with clinical pathological parameters. A total of 17 cases of NA were retrospectively studied to assess the immunohistochemical expression of p16 and its value for the diagnosis of this entity.

Nephrogenic adenoma of the prostate after laser therapy of benign prostatic hyperplasia

Nephrogenic adenoma (nephrogenic metaplasia) is a rare benign urological condition, which may present with hematuria, dysuria, and urinary frequency. In the prostatic urethra, it can be misdiagnosed as adenocarcinoma of the prostate. Risk factors for prostatic NA include trauma, infection and prior endourological procedures. We report a case of prostatic NA, presenting with isolated macroscopic hematuria in a man with a history of laser therapy of the prostate for benign prostate hyperplasia, and review the recent literature on the subject.

Nephrogenic adenoma of the bladder: a single institution experience assessing clinical factors

Introduction:

Nephrogenic adenoma (NA) was first described by Davis in 1949 as a “hamartoma” of the bladder. There are many proposed predisposing factors for NA including chronic inflammation, renal transplantation, and bladder cancer. We examined our experience with NA to determine predisposing factors and determine if there was any increased risk for development of subsequent malignancy.

Materials and Methods:

All patients with a pathologic diagnosis of bladder NA from 2001-2013 were included. Patient history, clinical factors including possible predisposing factors for NA, and follow-up were reviewed.

Results:

Among 60 patients, 68% were males with an average age of 61, an average BMI of 28.7, and 60% had a smoking history. In evaluating pro-inflammatory factors, 26.7% underwent either Bacillus Calmette-Guerin or mitomycin C, 30% had recurrent urinary tract infections, and 25% had a history of catheterization. Recurrence of NA after initial resection occurred only in 14.7% of patients who underwent follow-up cystoscopy. A history of concurrent bladder cancer was seen in 41.7% of patients, but there were no cases of de novo bladder cancer diagnosed after NA.

Conclusion:

To the best of our knowledge, this is the largest series of patients with NA of the bladder. NA occurs in a heterogeneous population of patients, but most often with underlying inflammation. NA occurred concurrent with bladder cancer; however there were no cases of de novo bladder cancer after NA, reassuring that NA is likely a benign reactive condition.

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

Nephrogenic adenoma (NA) is a rarely seen benign metaplastic lesion of the urinary tract. Its etiology is uncertain, but induced by chronic inflammation, irritation, and trauma. NA is located in the urinary tract, most commonly in the bladder. NA usually presents with hematuria and lower urinary tract symptoms. In the literature it is mostly seen in adults but about 30 cases of NA's have been reported in children. Treatment of intravesical lesions consists of transurethral resection (TUR) and fulguration and rarely partial or total cystectomy may be required in ineffective TUR. Recurrence rate is high during long-term follow-up. The intravesical application of sodium hyaluronate produces a protective effect on the glycosaminoglycan layer and delays or prevents its recurrence. We report a case of recurrent NA of the bladder in a pediatric male patient who was presented four years after previous surgery despite intravesical sodium hyaluronate therapy.

Nephrogenic Adenoma: Clinical Features, Management, and Diagnostic Pitfalls

OBJECTIVE

To review the diagnosis and management of nephrogenic adenoma (NA), an uncommon benign lesion found in the urinary tract. This lesion arises from a proliferation of implanted renal tubular cells. Although more common in adults, it can occur in all ages. NAs can recur and cause significant morbidity in patients. NAs are also a potential diagnostic pitfall as they can clinically and histologically mimic malignancy in the urinary tract.

MATERIALS AND METHODS

We performed an Institutional Board Review approved search of our surgical pathology database from 2005 to 2015 for cases of NA. A retrospective chart review was performed with a focus on the clinical, pathologic, and radiographic findings in these patients.

RESULTS

We identified 32 cases of NA in 31 patients. Lesions were most common in Caucasian males (male-to-female ratio of 2:1) with an average age at diagnosis of 55 years (range 25-77). Bladder was the most common site of occurrence (81.2%), followed by ureter (9.4%), urethra (6.3%), and intrarenal collecting system (3.1%). Most patients (72%) were symptomatic and presented with hematuria (41%), lower urinary tract symptoms (28%), pelvic or flank pain (6%), hydronephrosis (19%), or urinary incontinence (13%). NA was asymptomatic and identified incidentally in 9 (28%) patients. One patient (3%) had a renal transplant and 8 (26%) patients had diabetes mellitus. Twenty-six (84%) patients were managed with endoscopic resection of their tumors.

CONCLUSION

NAs are benign lesions that may cause significant morbidity and mimic malignant tumors. There should be increased suspicion in patients with predisposing factors.

Fibromyxoid nephrogenic adenoma protruding in a renal cortical cyst. A rare morphological variant in an outstanding location

Nephrogenic adenoma (NA) is an unusual, benign lesion of the urinary tract, generally presenting in the bladder and with less frequency in the renal pelvis, urethra or ureter. It consists of tubules, microcysts and papillae lined by a single layer of low cuboidal epithelium without atypia. Recently, a fibromyxoid variant mimicking an infiltrating mucinous adenocarcinoma has been described. We report hereby the case of a 70-year-old female with a fibromixoid NA protruding in a renal cortical cyst. Only one case of NA in a renal cortical cyst has been found in the literature and it was of the classical type. The development of a NA in a renal cortical cyst lends support to the theory that the NA results from proliferation of secondarily implanted exfoliated renal epithelial cells.

Recurrent nephrogenic adenoma in bladder diverticulum: Case report and literature review

Nephrogenic adenoma is an uncommon benign lesion of the urinary tract induced by chronic irritation of the vesical mucosa, due to infection, trauma, surgery, calculi, foreign bodies and chemical agents. A 68-year-old male was admitted to our linic for a periodical cystoscopic evaluation as part of a follow-up initiated due to a past transitional cell carcinoma. The scheduled cystoscopy revealed, within a bladder diverticulum, an unexpected and completely asymptomatic nephrogenic adenoma that we removed by transurethral resection. We followed up the patient at 24 months, then later we made the diagnosis of nephrogenic adenoma. During this time, the patient experienced three relapses within the same diverticulum, always involving a nephrogenic adenoma we persistently treated by transurethral resections. As the nephrogenic adenoma is considered a benign lesion without any direct evidence of a possible evolution to an overt cancer, we successful attempted a half-yearly cystoscopic follow-up to control the growth of a highly recurrent benign entity, interposing between controls a periodical imaging. This paper represents the second report of a nephrogenic adenoma within a bladder diverticulum, but the first case of a nephrogenic adenoma highly recurrent within the same diverticulum and managed conservatively by regular transurethral resection scheduled over the time.

Benign Diseases of the Bladder

Benign diseases of the bladder often present diagnostic challenges to practicing pathologists due to their diverse nature and ability to mimic a variety of epithelial or mesenchymal neoplasms. Categories of benign bladder disease include infectious cystitis, noninfectious cystitis, reactive proliferative processes, and benign processes that secondarily involve the bladder. An understanding of the key clinical and morphologic features of these lesions and the useful ancillary techniques specific for these entities is critical to the correct diagnosis of these lesions. This article reviews the key features of these benign bladder diseases and highlights methods to distinguish these lesions from other benign and malignant processes involving the bladder.

Fibromyxoid Nephrogenic Adenoma: A Newly Recognized Variant Mimicking Mucinous Adenocarcinoma

Nephrogenic adenomas demonstrate a variety of morphologic patterns that may occasionally be confused with malignant processes, including urothelial and prostatic carcinoma. In this series, we describe 8 cases of nephrogenic adenoma that contain an admixture of the classic tubular form of nephrogenic adenoma and an unusual spindled and fibromyxoid form of nephrogenic adenoma that closely mimics infiltrating carcinoma. In all cases, the classic tubular form of nephrogenic adenoma composed only a small proportion of the lesion, whereas the remainder consisted of compressed spindled cells within a fibromyxoid background, with only rare tubular and cordlike structures. On close examination, minimal nuclear atypia was identified in 2 cases, which included small, pinpoint nucleoli, and nuclear pseudoinclusions. All 8 patients were elderly men who had a prior or concurrent history of acinar prostate cancer (n=4), combined acinar prostate and urothelial carcinoma (n=1), urothelial-type adenocarcinoma of the prostate (n=1), bladder urothelial carcinoma (n=1), or no prior reported prostatic or urothelial abnormalities (n=1). Five patients received prior treatment with radiotherapy, 1 patient received intravesical mitomycin-C, and 1 also received bacillus Calmette-Guerin. The epithelial component of the lesions was positive in all cases for pancytokeratin (AE1/3) and racemase and demonstrated a variable cuff of type IV collagen surrounding the tubules. PAX-2 was positive with variable extent of labeling. Immunostains for prostate-specific antigen were negative. Histochemical stains identified some of the background matrix as mucin, with intense staining for periodic acid-Schiff and focal staining for mucicarmine. Stains for reticulin and amyloid (Congo red stain) and immunohistochemistry for Tamm-Horsfall protein were negative. This case series is the first report of a fibromyxoid subtype of nephrogenic adenoma. Awareness of this entity and the use of ancillary techniques can aid in the diagnosis of this unusual form of nephrogenic adenoma.

From the archives of the AFIP: Inflammatory and nonneoplastic bladder masses: radiologic-pathologic correlation

Although the vast majority of bladder tumors are epithelial neoplasms, a variety of nonneoplastic disorders can cause either focal bladder masses or diffuse mural thickening and mimic malignancy. Some of these entities are rare and poorly understood such as inflammatory pseudotumor, which produces ulcerated, bleeding polypoid bladder masses. These masses may be large and have an extravesical component. Bladder endometriosis manifests as submucosal masses with characteristic magnetic resonance imaging features consisting of hemorrhagic foci and reactive fibrosis. Nephrogenic adenoma has no typical features, and pathologic evaluation is required for diagnosis. Although imaging features of malacoplakia are also nonspecific, characteristic Michaelis-Gutmann bodies are found at pathologic evaluation. The various types of cystitis (cystitis cystica, cystitis glandularis, and eosinophilic cystitis) require pathologic diagnosis. Bladder infection with tuberculosis and schistosomiasis produces nonspecific bladder wall thickening and ulceration in the acute phase and should be suspected in patients who are immunocompromised or from countries where these infections are common. The diagnosis of chemotherapy cystitis and radiation cystitis should be clinically evident, but imaging may be used to determine severity and to assess complications. Extrinsic inflammatory diseases such as Crohn disease and diverticulitis may be associated with fistulas to the bladder and focal bladder wall abnormality. The extravesical findings allow the diagnosis to be made easily. Finally, extrinsic masses arising from the prostate or distal ureter may cause filling defects, which can be confused with intrinsic bladder masses.

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.

Nephrogenic adenoma of the urinary bladder: clinical experience and review of the literature

BACKGROUND

Nephrogenic adenoma (NA) is a rare disease of the urinary tract. We report our clinical experience with this disease in the urinary bladder and review the literature.

METHODS

Between April 1994 and July 2004, 8 patients were diagnosed with NA of the urinary bladder: 3 men and 5 women, aged 23-77 years (mean 49.6). Multiple predisposing factors were analyzed. The mean follow-up time was 56 months.

RESULTS

NA was not associated with transitional cell carcinoma in our series. All patients had recurrent urinary tract infection. Urinary tuberculosis was diagnosed in 2 patients. Two patients had undergone previous open urosurgery, and 4 patients had received previous endourologic management. A history of urolithiasis was found in 1 patient. Previous long-term urinary catheterization was noted in 3 patients. Two patients had received pelvic radiation therapy for cervical cancer. Urinary frequency and microscopic hematuria were found in all patients. All nephrogenic adenomas were treated with transurethral resection. Recurrent nephrogenic adenomas were diagnosed in 3 patients (median time to disease relapse, 7 months). Recurrent tumors were also treated with the endourologic method.

CONCLUSION

NA is an uncommon benign metaplastic lesion occurring in the urothelium. Transurethral resection of NA provides a definite diagnosis and relief of symptoms. The recurrence rate of NA is relatively high, so careful and long-term follow-up is necessary.

PAX2: a reliable marker for nephrogenic adenoma

Nephrogenic adenoma is a rare lesion of the urinary tract. The diagnosis usually is straightforward when characteristic microscopic and clinical findings are present, and the entity is familiar. However, misdiagnosis, in particular of adenocarcinoma of the prostate gland, may occur. Immunohistochemical stains often are needed to make such a distinction, but currently available markers offered only partial help. It recently was demonstrated that nephrogenic adenoma in renal transplant patients originated from the renal tubular epithelium. This newly proved, but long sought information may be helpful in the differential diagnosis of nephrogenic adenoma. In this study, we investigated the expression of a renal transcription factor, PAX2, in 39 nonrenal transplant-related nephrogenic adenomas, 100 adenocarcinomas of the prostate gland, and 47 urothelial carcinomas of the urinary tract. A strong and distinct nuclear staining of PAX2 was found in all 39 cases of nephrogenic adenoma (100%), but not in normal prostate tissue, normal urothelium, adenocarcinomas of the prostate gland, and invasive urothelial carcinomas. Focal CD10 was detected in six of 13 nephrogenic adenomas in the superficial papillary component and in normal prostate epithelium, normal urothelium, lymphocytes, adenocarcinoma of the prostate gland, and urothelial carcinoma. There was no uroplakins detected in nephrogenic adenoma. Therefore, these findings are suggesting that nephrogenic adenoma in nonrenal transplant patients may also arise from the renal epithelium, as did the comparable lesions after transplantation. PAX2 is a specific and sensitive immunohistochemical marker in identification and differential diagnosis of nephrogenic adenoma.

Nephrogenic Adenoma of the Urinary Bladder

INTRODUCTION

The nephrogenic adenoma (NA) is a benign metaplastic lesion of the urothelium and is attributed to chronic irritation of the mucosa, by injury, infection, stone disease or intravesical instrumentations. We present our experience on this morbid entity, its clinical appearance in the urinary bladder, its frequency and relapses. Furthermore we reviewed the related recent literature and focused on its potential to neoplastic degeneration and the value of the new diagnostic modalities.

PATIENTS AND METHODS

Four patients with NA of the urinary bladder are presented. The papilloid or polypoid formations observed by the cystoscopy were identified after the TUR, as NA of the urinary bladder. Their mean follow-up was 3.5 years.

RESULTS

Remission of the symptoms was observed after TUR in all patients. Three out of four patients presented 1-7 relapses, while in one case, after seven NA relapses, a urothelial carcinoma of the bladder was diagnosed.

CONCLUSIONS

Unlike histological features, the clinical - endoscopic characteristics of NA are non-specific. Even if it is not definitely considered like a premalignant condition, NA has to be followed up frequently and long lasting, because of its high recurrence rate. The combination of Cytology, Flow cytometry, DNA image analysis and Fluorescence in situ hybridization of bladder washings or voided urine, are of high value in monitoring NA of the urothelium.

Nephrogenic adenoma of the urinary bladder

INTRODUCTION

The nephrogenic adenoma (NA) is a benign metaplastic lesion of the urothelium and is attributed to chronic irritation of the mucosa, by injury, infection, stone disease or intravesical instrumentations. We present our experience on this morbid entity, its clinical appearance in the urinary bladder, its frequency and relapses. Furthermore we reviewed the related recent literature and focused on its potential to neoplastic degeneration and the value of the new diagnostic modalities.

PATIENTS AND METHODS

Four patients with NA of the urinary bladder are presented. The papilloid or polypoid formations observed by the cystoscopy were identified after the TUR, as NA of the urinary bladder. Their mean follow-up was 3.5 years.

RESULTS

Remission of the symptoms was observed after TUR in all patients. Three out of four patients presented 1-7 relapses, while in one case, after seven NA relapses, a urothelial carcinoma of the bladder was diagnosed.

CONCLUSIONS

Unlike histological features, the clinical--endoscopic characteristics of NA are non-specific. Even if it is not definitely considered like a premalignant condition, NA has to be followed up frequently and long lasting, because of its high recurrence rate. The combination of Cytology, Flow cytometry, DNA image analysis and Fluorescence in situ hybridisation of bladder washings or voided urine, are of high value in monitoring NA of the urothelium.

Expression of alpha-methylacyl-coenzyme A racemase in nephrogenic adenoma

Nephrogenic adenoma is a benign lesion composed of small glandular structures that develops along the urothelium with uncertain pathogenesis. Some investigators believe that nephrogenic adenoma develops by a metaplastic process in response to injury to the urothelium, while others believe that it arises from detached renal tubules. Nephrogenic adenoma may be present in the prostatic urethra and morphologically mimic prostatic adenocarcinoma. Alpha-methylacyl-coenzyme A racemase (AMACR), a recently identified prostate cancer marker, is typically negative in normal urothelium and prostatic glands, and positive in distal convoluted renal tubules in addition to prostatic adenocarcinomas. Therefore, evaluation of AMACR expression in nephrogenic adenoma will have significance in the pathologic diagnosis and in understanding pathogenesis of this lesion. We studied 38 nephrogenic adenomas by clinical, histologic, and immunohistochemical analyses for AMACR (P504S) and high molecular weight cytokeratin (34betaE12). Twenty-two of 38 nephrogenic adenomas (58%) demonstrated strong cytoplasmic positivity for AMACR, ranging from patchy, focal to diffuse staining. In addition, 16 of 26 (62%) nephrogenic adenomas were negative for 34betaE12. To our knowledge, this is one of the first report of a completely benign lesion, which can be found in the prostate, showing strong AMACR immunoreactivity. Our findings suggest using caution when interpreting positive AMACR immunostaining in prostatic specimens. These findings could be explained by possible renal tubular origin or renal differentiation, at least in a subset, of nephrogenic adenomas.

Nephrogenic adenoma of the prostatic urethra in a patient treated with ESWL for a lower ureteral stone

We present a case of prostatic urethral nephrogenic adenoma incidentally diagnosed in a patient treated with ESWL for ureteral stone disease, and we comment on this unusual urothelial lesion.

Derivation of nephrogenic adenomas from renal tubular cells in kidney-transplant recipients

BACKGROUND

Nephrogenic adenomas are benign, tumor-like lesions within the urothelial mucosa of the urinary tract that are not uncommon in renal-transplant recipients. We investigated the origin of nephrogenic adenomas in renal-transplant recipients.

METHODS

Tissue sections were analyzed by fluorescence in situ hybridization with the use of probes for the X and Y chromosomes, by immunohistochemical methods with the use of antibodies to renal tubular antigens, and by lectin histochemical methods. Forty-six nephrogenic adenomas from 29 patients were analyzed.

RESULTS

All nephrogenic adenomas in 14 female recipients of transplants from male donors and 10 male recipients of transplants from female donors showed the same sex-chromosome status as the donor kidney, but not the same sex-chromosome status as the recipient's surrounding bladder tissue. The nephrogenic adenomas from all 6 female recipients of transplants from female donors showed female chromosomes, and those from the 16 male recipients of transplants from male donors showed male chromosomes. The presence of aquaporin 1, PAX2, and lectin-binding capacity for peanut agglutinin, Lotus tetragonolobus agglutinin, and Sophora japonica agglutinin in nephrogenic adenomas indicated an origin from renal tubular cells.

CONCLUSIONS

Nephrogenic adenomas in renal-transplant recipients are derived from tubular cells of the renal transplants and are not metaplastic proliferations of the recipient's bladder urothelium.

[Nephrogenic bladder adenoma associated with glandular cystitis. Immunohistochemical study and significance]

A histopathological and immunohistochemical study of a case of nephrogenic adenoma of the bladder associated to glandular cystitis is presented with a very similar immunostaining to adenomatoid tumors in other organs and probably of a mesothelial origin. Its pathogenesis seems to correspond to a metaplastic change of the bladder's urothelium through anomalous differentiation of the reserve cells faced with different irritating agents. Because of its benign characteristics, we think that treatment can be confined to endoscopic observation and conservative technique.

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.

Nephrogenic adenoma of the prostatic urethra: a mimicker of prostate adenocarcinoma

Nephrogenic adenoma, thought to be a benign metaplastic response of the urothelium to injury, can rarely affect the prostatic urethra. Extension of small tubules of nephrogenic adenoma into the underlying prostatic fibromuscular stroma can lead to the misdiagnosis of prostatic adenocarcinoma in transurethral resection specimens and prostate biopsies. We reviewed 26 cases of nephrogenic adenoma involving the prostatic urethra, seen at The Johns Hopkins Hospital from 1990 to 1998, to evaluate the histologic features, which may better define this lesion. Immunohistochemical results were evaluated for cases where the lesion was present on deeper sections. Histologic patterns included the following: tubules in 96% (25 of 26), structures resembling vessels in 73% (19 of 26), cords and individual cells in 46% (12 of 26), papillary configurations in 19% (5 of 26), and signet ring cell-like tubules in 12% (3 of 26). Other features of nephrogenic adenoma, such as thyroidization, were identified in 38% (10 of 26), and peritubular sheaths were seen in 65% (17 of 26) of cases. Nucleoli were prominent in 54% (14 of 26), and no case had mitoses. In the region of nephrogenic adenoma, urothelium was noted in 69% (18 of 26); in 61% (11 of 18) it showed cuboidal metaplasia and 28% (5 of 18) showed squamous metaplasia. Extension of nephrogenic adenoma into muscle was observed in 77% (20 of 26) of cases, 75% (15 of 20) of which had identifiable urothelium overlying the lesion. Blue-tinged mucinous secretions were observed in 32% (8 of 25) of cases. Inflammation was found in all but one case. Nephrogenic adenomas were diffusely positive for 34betaE12 in 11% (1 of 9) of cases, focally positive in 44% (4 of 9), and negative in 44% (4 of 9). In 100% (9 of 9), cytokeratin 7 stains were positive. Focal prostate specific antigen and PSAP positivity were seen in 36% (4 of 11) and 50% (5 of 10) of nephrogenic adenoma cases, respectively. In conclusion, nephrogenic adenoma of the prostatic urethra can mimic prostate cancer because of: 1) the presence of tubules, cords, and signet ring-like tubules; 2) prominent nucleoli; 3) muscle involvement; 4) blue-tinged mucinous secretions; 5) focal prostate specific antigen and PSAP positivity; and 6) negative staining in some cases for 34betaE12. Features useful in the diagnosis of nephrogenic adenoma include the following: 1) distinctive nephrogenic patterns, such as papillary and "vascular," 2) adjacent urothelium, 3) thyroidization, 4) peritubular sheaths, 5) associated inflammation, and 6) positivity for cytokeratin 7 and, in some cases, 34betaE12.

Nephrogenic adenoma mimicking carcinoma: a potential pitfall in cytodiagnosis

Nephrogenic adenoma of the urinary bladder and urethra is an uncommon benign lesion of the urinary epithelium that can cytologically and histologically mimic malignancy. We report on the cytologic findings of a case of nephrogenic adenoma of the urethra that mimicked malignancy in an 84-yr-old woman. The differential diagnosis of this problematic lesion is discussed, and the literature describing the cytologic features is reviewed.