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Nephrogenic adenoma (NA) is an epithelial lesion that usually occurs in the mucosa of the urinary tract. Rare cases of deep infiltrative or perinephric lesions have also been reported. Recently, NA with characteristic fibromyxoid stroma (fibromyxoid NA) has been proposed as a distinct variant. Although shedding of distal renal tubular cells due to urinary tract rupture has been postulated as the cause of NA in general, the mechanism underlying extraurinary presentation of NA and fibromyxoid stromal change in fibromyxoid NA remains unknown. In this study, we performed mass spectrometry (MS) analysis in a case of perinephric fibromyxoid NA of an 82‐year‐old man who underwent right nephroureterectomy for distal ureteral cancer. The patient had no prior history of urinary tract injury or radiation. Periodic acid‐Schiff staining‐positive eosinophilic structureless deposits in the stroma of fibromyxoid NA were microdissected and subjected to liquid chromatography/MS. The analysis revealed the presence of a substantial amount of uromodulin (Tamm−Horsfall protein). The presence of urinary content in the stroma of perinephric fibromyxoid NA suggests that urinary tract rupture and engraftment of renal tubular epithelial cells directly cause the lesion. [ABSTRACT FROM AUTHOR]

Nephrogenic adenoma of the bladder in renal transplant patient -- case report. Nephrogenic adenoma (NA), also referred to as nephrogenic metaplasia, is a rare benign lesion affecting the urinary tract. The development of this lesion is attributed to the implantation of isolated renal tubular epithelial cells in areas of damaged transitional epithelium, often associated with prior instrumentation of the urinary tract. Clinical symptoms are nonspecific, commonly manifesting as hematuria (both macroscopic and microscopic), pollakisuria, and painful urination. Notably, during endoscopic examination, these lesions can be easily misinterpreted as malignant tumors. This publication presents two case reports of NA found in the urinary bladder of adult patients after kidney transplantation, the NAs faithfully mimicked urothelial carcinoma during cystoscopic and radiological examination. [ABSTRACT FROM AUTHOR]

Tissue-invasive cytomegalovirus (CMV) disease represents a well-recognized complication after kidney transplantation. However, direct involvement of the urogenital tract and CMV-ureteritis occur less frequently. Nephrogenic adenomas are benign lesions of the urinary tract preferentially reported in kidney transplant recipients. We herein report a second case of a 33-year-old male kidney transplant recipient with acute post-renal allograft dysfunction due to CMV-positive ureteral nephrogenic adenoma. A causal connection might be suspected but remains to be proven.

Ectopic prostatic tissue is rare, and it is usually only discovered by chance during imaging examinations or surgery. However, between 1967 and 2021, reports of ectopic prostatic tissue in the medical literature increased. It is rarely reported that ectopic prostatic tissue can be misdiagnosed as a nephrogenic adenoma (NA). This case study aimed to increase the awareness of ectopic prostatic tissue to improve its rates of diagnosis. This paper is focused on a 45-year-old male patient with a history of bladder lesions that were accidentally discovered through a health examination. A computed tomography scan revealed a homogeneous isoechoic mass in the posterior inferior wall of the bladder. At first, a transurethral cystoscopy revealed a smooth sessile mass covering the normal bladder mucosa, which was located in the middle of the interureteric ridge. The biopsy results suggested a possible intravesical NA. The mass was then completely resected under pneumovesicoscopy, and the pathological diagnosis was ectopic prostatic tissue. The clinical symptoms of ectopic prostatic tissue are similar to other bladder neoplasms, but there are too few characteristics available in imaging examinations to allow for an accurate diagnosis. Since ectopic prostatic tissue can present as a tumor in the bladder, urologists may easily misdiagnose the condition. Surgery is the basis of treatment for ectopic prostatic tissue, and it has a good prognosis. [ABSTRACT FROM AUTHOR]

Urethral strictures are a common cause of urinary obstruction which can be treated with surgical resection. Frozen sections are rare and pose a diagnostic challenge to pathologists due to the presence of benign lesions such as nephrogenic adenoma. We retrospectively examined all specimens of urethral stricture resections submitted to pathology at our institution from 2012 to 2022 (n = 258). Final pathology reports were searched to identify patients with dysplasia, carcinoma, or nephrogenic adenoma. When available, frozen section reports were also examined and compared to the final report, and additional clinical history and microscopic images were collected for patients with nephrogenic adenoma. Nephrogenic adenoma was identified in 3.8% (10/258) of urethral stricture resections. Dysplasia was identified in one patient who underwent two separate resections, and squamous cell carcinoma was found in one resection. Intraoperative frozen section was requested in 3.4% of resections (9/258). In two resections, an initial diagnosis of squamous cell carcinoma was initially favoured, however when reviewed with a genitourinary pathologist the diagnosis was changed to “reactive process” with a final diagnosis of nephrogenic adenoma. Nephrogenic adenoma can be challenging on frozen section due to variable architectural patterns, inflammation, and reactive changes. While urethral strictures are relatively common, their assessment by frozen section is rare and pathologists may lack familiarity with the variable morphology of benign entities that can be seen on frozen section resulting in their misinterpretation. We highlight this potential diagnostic pitfall and demonstrate the value of a second opinion prior to definitive frozen section diagnosis of malignancy. [ABSTRACT FROM AUTHOR]

Nephrogenic adenomas represent a suspected metaplastic response of the uroepithelium to chronic inflammation and are typically associated with recurrent urinary tract infections, stones, prior radiation therapy and other irritative factors, more commonly seen in adults. Nephrogenic adenoma (also known as nephrogenic metaplasia) usually involves the bladder in adults and represents a rare lesion that can easily be misdiagnosed as a malignancy. We present the case of a 14-year-old male with prior history of acute lymphoblastic leukemia (ALL) who presented with a several month history of vague flank pain which increased in intensity, leading to an emergency department presentation with the only significant finding on exam being microhematuria. Subsequent imaging showed a tumor like replacement of the right ureter with proximal hydronephrosis, initially felt to represent recurrent leukemia. Pathology revealed the tumor like ureteral replacement to represent a nephrogenic adenoma, a benign entity which often responds to conservative management, though not previously reported in the ureter in pediatrics.

Nephrogenic adenoma also referred to as nephrogenic metaplasia is a rare benign condition occurring most frequently in the urinary bladder. It is most commonly associated with chronic inflammation and genitourinary trauma and can present with a broad spectrum of histological features. It must be differentiated from malignant lesions, which can mimic both at cystoscopy and microscopically. Here, we report a case of nephrogenic adenoma in a middle-aged male with predisposing factors. [ABSTRACT FROM AUTHOR]

Nephrogenic adenoma (NA) is a benign, reactive lesion seen predominantly in the urinary bladder and often associated with antecedent inflammation, instrumentation, or an operative history. Its histopathologic diversity can create diagnostic dilemmas and pathologists use morphologic evaluation along with available immunohistochemical (IHC) markers to navigate these challenges. IHC assays currently do not designate or specify NA's potential putative cell of origin. Leveraging single-cell RNA-sequencing technology, we nominated a principal (P) cell-collecting duct marker, L1 cell adhesion molecule (L1CAM), as a potential biomarker for NA. IHC characterization revealed L1CAM to be positive in all 35 (100%) patient samples of NA; negative expression was seen in the benign urothelium, benign prostatic glands, urothelial carcinoma (UCA) in situ, prostatic adenocarcinoma, majority of high-grade UCA, and metastatic UCA. In the study, we also used single-cell RNA sequencing to nominate a novel compendium of biomarkers specific for the proximal tubule, loop of Henle, and distal tubule (DT) (including P and intercalated cells), which can be used to perform nephronal mapping using RNA in situ hybridization and IHC technology. Employing this technique on NA we found enrichment of both the P-cell marker L1CAM and, the proximal tubule type-A and -B cell markers, PDZKI1P1 and PIGR, respectively. The cell-type markers for the intercalated cell of DTs (LINC01187 and FOXI1), and the loop of Henle (UMOD and IRX5), were found to be uniformly absent in NA. Overall, our findings show that based on cell type-specific implications of L1CAM expression, the shared expression pattern of L1CAM between DT P cells and NA. L1CAM expression will be of potential value in assisting surgical pathologists toward a diagnosis of NA in challenging patient samples., (Copyright © 2024 The Authors. Published by Elsevier Inc. All rights reserved.)

Nephrogenic adenomas are benign lesions that develop within the urinary tract. Most often developing within the urinary bladder, these lesions have a debatable etiopathogenesis, with hamartoma, rest hyperplasia, and transplantation of renal tubular cells being the most widely accepted ones. Nephrogenic adenomas develop more often in adult males, and predisposing factors for their development are prior urinary system injury, infection, or malignancy, with a subset of cases developing in renal transplant patients. Herein, we present a case of a male patient in his seventies who initially presented to our institution with urinary disturbances and was subsequently diagnosed with low-grade, non-invasive urothelial carcinoma. After treatment, the patient remained disease-free for a period of seven calendar years. The current presentation was due to dysuria, and bladder endoscopy revealed a ureteral stricture and two small exophytic lesions neighboring the location of the previously treated urothelial carcinoma. Histology revealed complex papillary architecture and cystic spaces lined by a monolayer of monomorphous epithelial cells with foci of hobnail appearance. The papillary stroma consisted of edematous fibrous tissue with hyperemic blood vessels and focal infiltration by inflammatory cells. Based on the histological findings, the diagnosis of nephrogenic adenoma was established., Competing Interests: Human subjects: Consent was obtained or waived by all participants in this study. Conflicts of interest: In compliance with the ICMJE uniform disclosure form, all authors declare the following: Payment/services info: All authors have declared that no financial support was received from any organization for the submitted work. Financial relationships: All authors have declared that they have no financial relationships at present or within the previous three years with any organizations that might have an interest in the submitted work. Other relationships: The authors would like to disclose that one of the authors (George Stoyanov, MD, Ph.D.) was a member of the editorial approval board of the journal (Cureus Journal of Medical Science) at the time of the manuscript submission. The authors affirm that this in no way, shape, or form manipulated the reviewer selection process, reviews, or the initial or final editorial decision. ., (Copyright © 2024, Popov et al.)

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Nephrogenic adenoma is a rare benign urinary tract lesion. There are pediatric cases that have been managed with intravesical sodium hyaluronate, but there are no published adult cases. We present the first case of an adult successfully treated with intravesical sodium hyaluronate without resection. A 77-year-old man was investigated with cystoscopy for lower urinary tract symptoms (LUTS) unresponsive to medical therapy. This revealed multifocal flat black bladder lesions. Biopsy showed the lesions to be nephrogenic adenoma. His LUTS were treated with 6 weeks of intravesical sodium hyaluronate. He returned 6 weeks later for resection of his bladder lesions. However, resection was abandoned as the bladder lesions had entirely resolved. The resolution of the bladder lesions following intravesical sodium hyaluronate was unexpected but does agree with existing literature. The two reported pediatric cases also suggest that intravesical sodium hyaluronate is therapeutic for nephrogenic adenoma.

Tissue-invasive cytomegalovirus (CMV) disease represents a well-recognized complication after kidney transplantation. However, direct involvement of the urogenital tract and CMV-ureteritis occur less frequently. Nephrogenic adenomas are benign lesions of the urinary tract preferentially reported in kidney transplant recipients. We herein report a second case of a 33-year-old male kidney transplant recipient with acute post-renal allograft dysfunction due to CMV-positive ureteral nephrogenic adenoma. A causal connection might be suspected but remains to be proven., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2024 Hosek, Montani and Mani.)

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 (NA) is a rare, benign proliferation of glands of the urinary tract, usually occurring as a result of chronic inflammation, trauma or other similar chronic injuries to the urothelial mucosa. We aimed to share two pediatric cases diagnosed with NA in our hospital between the years 2010 and 2016. The first case was polypoid type NA of the bladder and the second case was fibromyxoid NA of the urethra.

Nephrogenic adenoma is a rare benign urinary tract lesion. There are pediatric cases that have been managed with intravesical sodium hyaluronate, but there are no published adult cases. We present the first case of an adult successfully treated with intravesical sodium hyaluronate without resection. A 77-year-old man was investigated with cystoscopy for lower urinary tract symptoms (LUTS) unresponsive to medical therapy. This revealed multifocal flat black bladder lesions. Biopsy showed the lesions to be nephrogenic adenoma. His LUTS were treated with 6 weeks of intravesical sodium hyaluronate. He returned 6 weeks later for resection of his bladder lesions. However, resection was abandoned as the bladder lesions had entirely resolved. The resolution of the bladder lesions following intravesical sodium hyaluronate was unexpected but does agree with existing literature. The two reported pediatric cases also suggest that intravesical sodium hyaluronate is therapeutic for nephrogenic adenoma. [ABSTRACT FROM AUTHOR]

Background Nephrogenic adenoma is an uncommon benign lesion that occurs at several sites in urinary tract, from the renal pelvis to urethra, with the highest frequency in urinary bladder. Nephrogenic adenoma displays a broad spectrum of architectural and cytological features. Hence, recognition of its characteristic histopathological features is needed to distinguish this lesion from its mimickers. Materials and methods A retrospective series of 21 cases of nephrogenic adenoma in 18 patients, which were diagnosed in our department between 2010 and 2016, were analyzed. All histological slides were reviewed by two pathologists and the diagnosis of each case was confirmed. Immunohistochemistry was performed for PAX-8 in all cases. CK7, PAX-2, PSA, p53, p63, GATA-3 and α-methylacyl-CoA racemase (AMACR) were applied in problematic cases. Results The most common location of the lesion was urinary bladder (14 patients) followed by renal pelvis (2 patients), ureter (1 patient) and urethra (1 patient). A history of urothelial carcinoma and repeated TUR procedures were observed in 12 patients. There were 2 pediatric patients aged 3 years. Both of them had undergone previous urosurgery because of megaureter in one and bladder exstrophy in the other. Other clinical antecedents included bladder diverticulum (1 patient), cystitis (1 patient) and nephrolithiasis (1 patient). Recurrence of lesion was seen in two patients (once in one case and twice in the other one). The median time to disease recurrence in these patients was 11 months (range, 2–20 months). Histologically, the lesions exhibited various morphological findings, with mixed (15 cases, 71.4%), pure tubular (3 cases, 14.3%), pure papillary (2 cases, 9.5%) and pure flat (1 case, 4.8%) growth patterns. Of the 15 cases with mixed patterns, 8 cases were tubulocystic and flat, 3 cases were tubular and flat, 2 cases were tubular, papillary and flat, 1 case was tubulocystic, papillary and flat, and 1 case was tubular and papillary. Flat pattern was observed in 15 cases (71.4%). It was seen in association with other patterns in 14 cases (mixed morphology) and purely in 1 case. Our findings suggested that the flat pattern is a frequent finding in nephrogenic adenomas. Notably one case in this series showed superficial extension into bladder muscularis propria. Conclusions Histologically nephrogenic adenoma may simulate a variety of malignancies. Awareness of characteristic morphologic features of nephrogenic adenoma is needed to diagnose this lesion correctly. [ABSTRACT FROM AUTHOR]

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., Competing Interests: The authors have declared that no competing interests exist., (Copyright © 2023, Alvarez Moreno et al.)

Nephrogenic adenoma (NA) is a rare, benign proliferation of glands of the urinary tract, usually occurring as a result of chronic inflammation, trauma or other similar chronic injuries to the urothelial mucosa. We aimed to share two pediatric cases diagnosed with NA in our hospital between the years 2010 and 2016. The first case was polypoid type NA of the bladder and the second case was fibromyxoid NA of the urethra. [ABSTRACT FROM AUTHOR]

Nephrogenic adenoma (NA), referred to as nephrogenic metaplasia, is a rare benign lesion of the urinary tract. NA is histologically characterized by tubular and papillary formations lined by low cuboidal to columnar epithelial cells. NA is also immunohistochemically characterized by positivity for paired box (PAX) 2, PAX8 and cytokeratin 7, and negative for P63 and prostate-specific antigen. In this study, we present 3 cases of NA arising in the urinary bladder of elderly male patients with predisposing factors: Patient 1 had undergone transurethral lithotripsy due to a ureteral stone; patient 2 had undergone transurethral resection of a urothelial carcinoma in the urinary bladder; and patient 3 had been treated with Bacillus-Calmettle-Guérin due to a urothelial carcinoma in the urinary bladder. The characteristics of the NAs of our 3 cases were histologically and immunohistologically consistent with previously reported cases, although 1 patient exhibited a pseudoinvasive pattern. Since NA is a tumor-like benign lesion, it should be clearly differentiated morphologically and immunohistologically from other tumors arising in the urinary tract and from invasion by prostate cancer. [ABSTRACT FROM AUTHOR]

Objectives: The aim of this study is to determine if the diagnosis of nephrogenic adenoma (NA) can be made on cytologic criteria alone and if pair box gene transcription factor 8 (PAX8) is useful in the diagnosis of NA in daily cytology practice.Methods: Cytologic features of NA previously described in a literature were used to identify NA cells in urinary specimens. Subsequently, all cytology and corresponding biopsy specimens were stained with the PAX8 immunohistochemistry stain. The stains were examined; the results were tabulated.Results: A total of 44 specimens were reviewed (35 with corresponding biopsy specimens diagnosed as NA and nine negative for NA diagnosis on corresponding biopsy specimens). Of them, 14 demonstrated features previously described as NA. None of atypical cells that were morphologically suspicious for NA showed positive staining, whereas all of the corresponding biopsy sections demonstrated nuclear PAX8 positivity. Only rare lymphocytes present in cytology specimens showed nuclear staining with PAX8.Conclusions: Assuming that the results of the PAX8 stain performed are accurate at least in most cases, as suggested by the presence of internal positive controls, our study shows that the previously described cytologic features of NA cannot be used as diagnostic criteria, since they are not characteristic for this entity. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Background: Patients following solid organ transplantation have an increased risk of developing de novo bladder tumors, but their biology is poorly characterized. Methods: We studied 1743 patients who underwent a transurethral resection of a newly diagnosed bladder tumor at a single institution. The histopathology, treatment, recurrence-free survival and overall survival were evaluated and compared between transplant and non-transplant patients. Results: We identified 74 transplant patients who developed a de novo bladder tumor after a median post-transplantation interval of 62 months. The tumor was malignant in 29 patients (39 %). The most common benign lesion was nephrogenic adenoma (84 %), which neither coexisted with nor developed into malignant tumors during follow-up. Compared with non-transplant patients ( n = 1669), transplant patients were significantly younger (median 55 vs 69 years, P < 0.001) and had a 9.0-fold higher odds of benign tumors ( P < 0.001), while there were no differences in pathology among patients with urothelial carcinoma of the bladder (UCB). In a multivariable analysis for non-muscle-invasive UCB that was adjusted for the risk group, patients with a transplant had a 1.8-fold increased risk of recurrence ( P = 0.048). Four of five transplant patients did not respond to Bacillus Calmette-Guérin instillations. There were no differences in overall survival after radical cystectomy ( P = 0.87). Conclusions: The majority of bladder tumors in transplant patients are benign, and they neither coexist with nor develop into malignant tumors. Transplant patients with non-muscle-invasive UCB show an increased risk of disease recurrence, while those treated with radical cystectomy have similar outcomes to patients without a transplant. [ABSTRACT FROM AUTHOR]

Urethral cancer is a rare malignancy with urothelial subtype being the most common followed by adenocarcinoma. In women, the usual presentation is urinary retention and hematuria. Clear cell variety of adenocarcinoma is a rarer entity which usually has a better prognosis than other variants. Lymph node metastasis is seen in about 30% of urethral cancers. Histopathological differential diagnosis includes Skene gland carcinoma and nephrogenic adenoma. Herein, we present a 58-year-old female patient who presented for evaluation of lymph node mass in the inguinal region. The detailed evaluation revealed clear cell adenocarcinoma of the urethra as the primary with lymph node metastasis. [ABSTRACT FROM AUTHOR]

Nephrogenic adenoma is a rare, benign, metaplastic lesion predominantly seen in urinary bladder, which occurs even more rarely in the ureters. We report two such cases, arising in the ureter. Both patients were young adult males. Histology of both cases was similar, showing tubules lined by columnar cells with hobnailing of nuclei. Immunohistochemically, both cases resembled their counterparts in urinary bladder. These lesions are important to recognize, since they can easily be confused with several malignancies.