Immunohistochemical Staining Characteristics of Nephrogenic Adenoma Using the PIN-4 Cocktail (p63, AMACR, and CK903) and GATA-3

Expression of L1 Cell Adhesion Molecule, a Nephronal Principal Cell Marker, in Nephrogenic Adenoma

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.

Identification of uromodulin deposition in the stroma of perinephric fibromyxoid nephrogenic adenoma by mass spectrometry

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.

The Application and Pitfalls of Immunohistochemical Markers in Challenging Diagnosis of Genitourinary Pathology

CONTEXT.—

The morphologic features of different entities in genitourinary pathology overlap, presenting a diagnostic challenge, especially when diagnostic materials are limited. Immunohistochemical markers are valuable when morphologic features alone are insufficient for definitive diagnosis. The World Health Organization classification of urinary and male genital tumors has been updated for 2022. An updated review of immunohistochemical markers for newly classified genitourinary neoplasms and their differential diagnosis is needed.

OBJECTIVE.—

To review immunohistochemical markers used in the diagnosis of genitourinary lesions in the kidney, bladder, prostate, and testis. We particularly emphasized difficult differential diagnosis and pitfalls in immunohistochemistry application and interpretation. New markers and new entities in the 2022 World Health Organization classifications of genitourinary tumors are reviewed. Recommended staining panels for commonly encountered difficult differential diagnoses and potential pitfalls are discussed.

DATA SOURCES.—

Review of current literature and our own experience.

CONCLUSIONS.—

Immunohistochemistry is a valuable tool in the diagnosis of problematic lesions of the genitourinary tract. However, the immunostains must be carefully interpreted in the context of morphologic findings with a thorough knowledge of pitfalls and limitations.

Clear Cell Papillary Renal Cell Tumors: A Study of 42 Tumors with Emphasis on the Fibrous Capsule, Cystic Component, and GATA3 Immunohistochemistry

Clear cell papillary renal cell tumor is a common and sometimes underdiagnosed renal cell neoplasm. Its proper recognition is important because its diagnosis implies a remarkably high probability of indolent behavior. This study aimed to evaluate the frequency of a fibrous capsule, a cystic component, and a GATA3 expression in clear cell papillary renal cell tumors. We assessed 419 renal cell neoplasms from three institutions located in northeastern Brazil and identified 42 clear cell papillary renal cell tumors (from 39 patients), which were the fourth most common renal cell neoplasm. These tumors commonly exhibited fibrous capsules (all showed complete or partial capsules) and cystic component (93%). Eighteen out of 42 tumors (43%) showed some expression of GATA3, and weak and focal staining was common among the positive tumors. Clear cell papillary renal cell tumor must always be included in the differential diagnosis of predominantly cystic renal cell neoplasms. As GATA3 is inconsistently expressed in clear cell papillary renal cell tumors, it is not useful in this diagnosis.

Nephrogenic adenoma of the renal pelvis: A rare case report and review of the literature

RATIONALE

Nephrogenic adenoma (NA) is a rare benign lesion of the urinary tract, which rarely occurs in the renal pelvis. Only 19 cases have been reported in the literature. However, there is no detailed report on the clinicopathological features of NA of the renal pelvis.

PATIENT CONCERNS

This case report describes a 46-year-old male patient who was admitted to the hospital for one month because of painless gross hematuria with blood clots. He had a history of hyperuricemia and a family history of gastric cancer.

DIAGNOSES

NA of the renal pelvis was diagnosed pathologically and immunohistochemical.

INTERVENTIONS

The patient underwent laparoscopic nephroureterectomy.

OUTCOMES

The patient recovered well after the operation with no discomfort. In addition, we followed up with the patient regularly post-discharge (approximately 20 months). There were no obvious abnormalities in the results of routine urine culture, computed tomography scan of the abdomen, and cystoscopy during the follow-up period, and the symptoms disappeared completely and did not recur.

LESSONS

NA of the renal pelvis is extremely rare in the clinic, which can be easily misdiagnosed and overtreated. However, for pathological diagnosis of this disease, specific immunohistochemical staining for preoperative biopsy was reported to be significant, which should be considered by the urologists and pathologists.

Classification of renal cell tumors – current concepts and use of ancillary tests: recommendations of the Brazilian Society of Pathology

Classification of renal cell carcinomas has become more challenging. The 2016 WHO classification included 14 different subtypes and 4 emerging/provisional entities, and recent literature indicates new entities to be incorporated. Nomenclature is based on cytoplasmic appearance, architecture, combination of morphologies, anatomic location, underlying disease, familial syndromes, and specific genetic alterations. Immunohistochemistry is useful in selected cases while it can be insufficient in entities that require molecular confirmation of a specific gene alteration. The aim of these recommendations is to provide a reasonable and optimized approach for the use of ancillary tests in subtyping renal tumors, particularly in resource-limited settings.

Napsin A is a highly sensitive marker for nephrogenic adenoma: an immunohistochemical study with a specificity test in genitourinary tumors

Nephrogenic adenomas are uncommon benign lesions that are typically cytologically bland, but degenerative and reactive changes may make it difficult to distinguish these lesions from malignant entities, such as urothelial carcinoma and prostatic adenocarcinoma. In this study, we explored whether napsin A, a sensitive marker for lung adenocarcinoma, may also have a role in distinguishing nephrogenic adenoma from other genitourinary lesions. Immunohistochemically, napsin A was expressed in all 43 nephrogenic adenomas (bladder: 38, prostatic urethra: 4, and ureter: 1; mean positive tumor cells: 72%, median: 80%, range: 15-100%) and showed regional variability in its expression pattern with a bias toward surface architectures (flat, papillary) compared with stromal architectures (tubular/glandular, microcystic). We also compared napsin A with other markers including PAX8, GATA3, p63, and 34BE12. Although napsin A matched PAX8 in terms of its sensitivity for nephrogenic adenoma (100%), napsin A stained a lower percentage of tumor cells than PAX8 (72% vs 99%, respectively, P = 1.0 × 10^-5). P63 was negative in all nephrogenic adenomas, whereas GATA3 showed variable staining in 25 cases (58%). All 43 nephrogenic adenomas showed variable 34BE12 staining. Finally, we profiled napsin A expression among 401 genitourinary tumors on tissue microarrays (n = 308) and full tissue blocks (N = 93) and observed napsin A positivity in 37 tumors (9%), which included urothelial carcinomas with the glandular/microcystic component differentiation (in the glandular/microcystic component in 4/6), bladder adenocarcinomas (primary: 4/4 and metastatic: 3/3), urinary tract clear-cell carcinomas (primary: 8/9, metastatic uterine primary: 1/1), and some renal tumors (17/174). All 81 pure urothelial carcinomas and 53 prostatic acinar adenocarcinomas were negative for napsin A. Our study indicates that napsin A is a highly sensitive marker for nephrogenic adenoma and can serve as a useful addition in immunohistochemical panels seeking to distinguish it from pure urothelial carcinoma and prostatic acinar adenocarcinoma but not clear-cell carcinoma or urothelial carcinoma with glandular differentiation.

PAX8 expression and TERT promoter mutations in the nested variant of urothelial carcinoma: a clinicopathologic study with immunohistochemical and molecular correlates

The nested variant of urothelial carcinoma, a frequent mimic of benign lesions on limited specimens, has been associated with high-stage disease including metastases at presentation. While PAX8 immunohistochemistry has been noted to be infrequently present in urothelial carcinoma in general, it has not been studied specifically in a cohort of nested urothelial carcinomas. Furthermore, TERT promoter mutation status is a potentially valuable biomarker for diagnosis of urothelial carcinoma and for noninvasive disease monitoring that has been observed in a majority of urothelial carcinoma and has previously been seen to be prevalent in multiple variant morphologies of urothelial carcinoma, including the nested variant. Twenty-five primary and three metastatic samples of nested urothelial carcinoma, along with 16 benign cases, were identified in a multicenter retrospective record review. PAX8 immunohistochemical stain was performed on all cases. In addition, TERT mutation analysis by allele-specific PCR was performed on 21 of the primary nested urothelial carcinoma cases and all benign cases. Positive PAX8 expression was identified in 52% (13 of 25) primary cases and 67% (2 of 3) metastatic cases of nested urothelial carcinoma; 50% (1 of 2) cases of large nested urothelial carcinoma were positive for PAX8. PAX8 expression was negative in the benign urothelium in all cases. TERT promoter mutation was observed in 83% (15 of 18) nested urothelial carcinoma cases and in 6% (1 of 16) of the benign cases. Recognition of the prevalence of positive PAX8 staining in this clinically relevant variant of urothelial carcinoma is essential to avoiding inaccurate or delayed diagnosis during the diagnostic workup of bladder lesions suspicious for nested variant of urothelial carcinoma. Moreover, the prevalence of TERT promoter mutations in nested urothelial carcinoma is similar to that of conventional urothelial carcinoma, further supporting its use as a biomarker that is stable across morphologic variants of urothelial carcinoma.

The applicability and utility of immunohistochemical biomarkers in bladder pathology

Urinary bladder specimens are frequently encountered in the daily practice of surgical pathologists. The spectrum of pathologic entities encountered in bladder specimens is extraordinarily broad, and in some instances, immunohistochemical stains are used to help characterize challenging bladder lesions. Cost-effective biomarker selection tailored to the differential diagnosis facilitates an accurate diagnosis. This comprehensive review is prepared as a reference guide for the use of immunohistochemistry to categorize primary and secondary bladder neoplasms and to evaluate metastatic cancers for possible bladder origin.

Common and uncommon features of nephrogenic adenoma revisited

Nephrogenic adenoma is a common diagnosis in urological pathology that may be challenging for general pathologists. Due to its polymorphic appearance under the microscope, some cases can be misdiagnosed as malignancy and then unnecessarily overtreated. Aside from the typical tubules, cysts and papillae, nephrogenic adenoma may display a broad spectrum of histologic appearances and locations, some of them atypical or unexpected. These unusual and concerning features will have special consideration in this description. The goal of the review is to increase awareness of general pathologists of the varied histology of nephrogenic adenoma.

Iatrogenic Disease of the Genitourinary Tract

Iatrogenic disease is defined as illness caused by diagnostic procedures or treatment given by health care professionals. More recently described treatment complications involving the genitourinary tract include newly recognized variants of renal carcinoma in the setting of dialysis/end-stage renal disease, treatment effect in genitourinary carcinomas, and medical renal disease caused by drug therapies, including immunotherapy. The objective of this review is to cover iatrogenic inflammatory diseases, pseudotumors and tumors of the kidney, bladder, prostate, testis and paratestis of most interest to surgical pathologists. For this reason, disease caused by the following will not be covered: iatrogenic glomerulonephritis, self-inflicted injury including the introduction of foreign bodies, surgical error, drugs of abuse and herbal medications, and iatrogenic disease in the transplant setting including ischemia/reperfusion injury. Emphasis is placed upon commonly encountered diseases in order to ensure that the review is of utility to practicing pathologists. The clinical context, pathophysiology and histopathology of each disease entity are covered.

Molecular Pathology of High-Grade Prostatic Intraepithelial Neoplasia: Challenges and Opportunities

A better understanding of the early stages of prostate cancer initiation, potentially arising from precursor lesions, may fuel development of powerful approaches for prostate cancer prevention or interception. The best-known candidate for such a precursor lesion has been referred to as high-grade prostatic intraepithelial neoplasia (HGPIN). Although there is significant evidence supporting the notion that such HGPIN lesions can give rise to invasive adenocarcinomas of the prostate, there are also numerous complicating considerations and evidence that cloud the picture in many instances. Notably, recent evidence has suggested that some fraction of such lesions that are morphologically consistent with HGPIN may actually be invasive carcinomas masquerading as HGPIN-a state that we term "postinvasive intraepithelial carcinoma" (PIC). Although the prevalence of such PIC lesions is not fully understood, this and other factors can confound the potential of identifying prostate precursors that can be targeted for disease prevention, interception, or treatment. Here, we review our current understanding of the morphological and molecular pathological features of prostate cancer precursor lesions.

Contemporary Grading and Staging of Urothelial Neoplasms of the Urinary Bladder: New Concepts and Approaches to Challenging Scenarios

Grading and staging of urothelial neoplasm are the most crucial factors in risk stratification and management; both necessitate optimal accuracy and consistency. Several updates and recommendations have been provided though recent publications of the 4th edition of the World Health Organization classification, the 8th edition of the American Joint Committee on Cancer staging system, and the International Consultation on Urological Diseases-European Association of Urology updates on bladder cancer. Updates and recent studies have provided better insights into and approaches to the challenging scenarios in grading and staging of urothelial neoplasm; however, there remain aspects that need further investigation and refinement.

Immunohistochemical Pitfalls in Genitourinary Pathology: 2018 Update

Immunohistochemistry may be a very useful adjunct to morphologic diagnosis in many areas of surgical pathology, including genitourinary pathology. In this review, we address common diagnostic dilemmas where immunophenotypic analysis may be utilized and we highlight pitfalls specific to each scenario. For prostate, we review the diagnosis of limited prostatic adenocarcinoma and the distinction of high-grade prostatic adenocarcinoma from urothelial carcinoma. We also cover markers of urothelial lineage in the diagnosis of metastatic carcinoma of unknown primary site. In the kidney, distinction of poorly differentiated renal cell carcinoma from urothelial carcinoma and epithelioid angiomyolipoma, adjuncts to the recognition of hereditary renal neoplasia, and the diagnosis of metastatic renal cell carcinoma are discussed. Finally, for testis we address distinction of germ cell tumors from sex cord-stromal tumors, as well as the diagnosis of metastatic germ cell tumors.

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.

Can We Identify Nephrogenic Adenoma in Urine Cytology Specimens? A Study Evaluating Previously Described Cytomorphologic Features in Correlation With PAX8 Immunohistochemical Staining Results

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.