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

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.

Mullerian Duct-Type Clear Cell Adenocarcinoma of the Urethra in a Woman Presenting As Groin Swelling

Primary Mullerian duct-type clear cell adenocarcinoma of the urethra is a rare clinical entity with a varied clinical presentation. This can be diagnosed only with a high index of suspicion. Clinical examination, biopsy, and immunohistochemistry are essential for diagnosis. Management will need a multimodal approach with a combination of chemotherapy and surgical excision.

Case report: Renal adenoma in a captive ocelot (Leopardus pardalis) in Costa Rica

Reports of renal neoplasia are rare in neotropical wildcats. Ocelots (Leopardus pardalis) are medium-sized wildcats living in America's tropical forests. A 12-year-old captive ocelot was diagnosed with a renal mass occupying approximately 25% of the total right kidney volume. The tissue was stained with routine hematoxylin and eosin (H&E) and periodic acid-Schiff (PAS). Immunohistochemistry with the following markers was performed: cytokeratin (CK) AE1/AE3, CK19, CK 7, CD10, vimentin, Melan A, HMB45, Pax-8, and Wilms' tumor 1 (WT1). Histopathology revealed a well-differentiated epithelial tubular neoplasia with less than one mitotic figure per 2.37mm2 field. Vimentin and Pax-8 were the only positive markers. Immunohistochemically, neoplasia was diagnosed as a renal adenoma. Renal adenomas are seldom reported in neotropical wildcats. Reports on wild species are valuable for properly establishing a clinical prognosis for captive species. To the best of our knowledge, this is the first report that provides detailed microscopic and immunohistochemical descriptions of renal adenoma in a captive ocelot.

Pax-8: Molecular biology, pathophysiology, and potential pathogenesis

Transcription factors, as the convergence points of multiple signaling pathways in eukaryotic cells, are closely involved in disease development. Pax-8, an important transcription factor belonging to the Pax family, exerts a crucial influence on the regulation of gene expression required for both physiological conditions and pathological processes. Pax-8 contributes to the pathogenesis of many human diseases, ranging from cardiovascular disease to many cancers, and therefore, it can be imagined that Pax-8 holds great therapeutic potential. In this review, we summarize the structure, distribution, function, and regulatory mechanisms of Pax-8 to provide a new research direction for Pax-8.

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.

A Rare Case of Urinary Bladder Hamartoma Clinically Mimicking an Urothelial Carcinoma: A Case Report and Review of the Literature

Urinary bladder hamartoma is a rare benign proliferation with only 14 cases reported in the literature at present. Urinary bladder hamartoma is composed of a disorderly admixture of normal urinary bladder components, essentially represented by glands lined by transitional epithelium and a variable percentage of fibrous stroma, smooth muscle bundles, and adipose tissue. Urinary bladder hamartomas do not exhibit cytological or architectural abnormalities and show no necrosis or increase in mitotic activity. Clinical manifestations are usually represented by lower urinary tract symptoms, more or less frequently paired with gross hematuria. Several pediatric cases of urinary bladder hamartoma have been reported, sometimes with syndromic associations. Transurethral resection has been curative in all cases reported, with no evidence of recurrence. Here we report an additional rare urinary bladder hamartoma, clinically mimicking urothelial carcinoma, providing a review of the literature regarding this unusual entity.

Ureteral Metastasis of Colonic Adenocarcinoma with Enteroblastic Differentiation: A Rare Case to be Distinguished from Clear Cell Adenocarcinoma of the Urinary Tract

Adenocarcinomas with enteroblastic differentiation are rare clear cell tumors that are positive for enteroblastic markers. Enteroblastic differentiation is particularly uncommon in colorectal adenocarcinomas. Herein, we report a case of clear cell adenocarcinoma with enteroblastic differentiation in the sigmoid colon of a 38-year-old Japanese woman that metastasized to the lower left ureter. After neoadjuvant chemotherapy, the patient underwent low anterior resection. The tumor consisted of tubular, cribriform, and focal micropapillary proliferation of clear cells immunopositive for spalt-like transcription factor 4 (SALL4), glypican 3, and alpha-fetoprotein. Six months after the colonic resection, a tumor was found in the left lower ureter, which was resected. The ureteral tumor revealed clear cell adenocarcinoma, which was identical to the colonic tumor proliferating in the ureteral mucosa. Metastatic ureteral tumors are rare. We performed a literature search and found only 50 reported cases of ureteral metastases from colorectal cancer. Of these, only 10 metastatic tumors were identified in the ureteral mucosa. No case of ureteral metastasis of clear cell colorectal adenocarcinoma or colorectal adenocarcinoma with enteroblastic differentiation has been reported. Hence, it can be challenging to distinguish them from clear cell adenocarcinoma of the urinary tract and/or clear cell urothelial carcinoma. This paper discussed the differential diagnosis of these tumors and reviewed the clinicopathological features of colorectal carcinomas metastasizing to the ureter.

Cadherin-16 (CDH16) immunohistochemistry: a useful diagnostic tool for renal cell carcinoma and papillary carcinomas of the thyroid

Cadherin-16 (CDH16) plays a role in the embryonal development in kidney and thyroid. Downregulation of CDH16 RNA was found in papillary carcinomas of the thyroid. To determine the expression of CDH16 in tumors and to assess the diagnostic utility a tissue microarray containing 15,584 samples from 152 different tumor types as well as 608 samples of 76 different normal tissue types was analyzed. A membranous CDH16 immunostaining was predominantly seen in thyroid, kidney, cauda epididymis, and mesonephric remnants. In the thyroid, CDH16 staining was seen in 100% of normal samples, 86% of follicular adenomas, 60% of follicular carcinomas, but only 7% of papillary carcinomas (p < 0.0001). CDH16 positivity was frequent in nephrogenic adenomas (100%), oncocytomas (98%), chromophobe (97%), clear cell (85%), and papillary (76%) renal cell carcinomas (RCCs), various subtypes of carcinoma of the ovary (16-56%), various subtyped of carcinomas of the uterus (18-40%), as well as in various subtypes of neuroendocrine neoplasms (4-26%). Nineteen further tumor entities showed a weak to moderate CDH16 staining in up to 8% of cases. Our data suggest CDH16 as a potential diagnostic marker-as a part of a panel-for the identification of papillary carcinomas of the thyroid, nephrogenic adenomas, and the distinction of renal cell tumors from other neoplasms.

CDX2- and PAX8-Expressing Subtypes in Female Urethral Adenocarcinoma: Pathogenesis Insights through Immunohistochemical and Morphological Analyses

Female urethral adenocarcinoma has attracted attention as a rare tumor type based on its differential pathogenesis from its male counterpart. However, to date, our knowledge concerning its immunohistochemical and morphological characteristics remains limited due to the small number of cases studied. In this study, nine consecutive cases of female urethral adenocarcinoma were used for immunohistochemical and morphological characterization of the tumor based on semi-comprehensive immunohistochemical analysis and detailed morphological evaluations. Our immunohistochemical assay revealed two subtypes of female urethral adenocarcinoma with distinctive staining patterns: the CDX2- and PAX8-expressing subtypes. The former stained positive for other intestinal markers (e.g., HNF4α and TFF1) as well (7 of 7 cases); the latter stained negative for these intestinal markers (0 of 2 cases) but stained positive for clear cell carcinoma markers (e.g., Napsin A and HNF1β) (2 of 2 cases). Regarding cytokeratins, the former displayed a CK7- and CK20-positive immunoprofile (7 of 7 cases); the latter exhibited a CK7-positive and CK20-negative immunoprofile (2 of 2 cases). Morphologically, CDX2- and PAX8-expressing subtypes resembled intestinal-type adenocarcinoma and clear cell carcinoma (occurring in gynecological organs), respectively. The semi-comprehensive immunoprofiling data presented in this study can potentially contribute to the correct diagnosis of this rare tumor type. Finally, our study represents an important basis for future investigations aiming to further elucidate the details and origin of female urethral adenocarcinoma, and it can potentially contribute to developing diagnostic and therapeutic strategies for treating this malignancy.

GATA3 expression in clear cell adenocarcinoma of the lower urinary tract: a potential diagnostic pitfall

BACKGROUND

Clear cell adenocarcinoma of the lower urinary tract (CCACLUT) is a rare primary malignant neoplasm with heterogenous morphology. There is a paucity of data in the literature regarding its immunohistochemical profile.

METHODS

The immunohistochemical features (extent and intensity) of a multinational cohort of CCACLUT were evaluated with comparison between clear cell adenocarcinoma of the female genital tract (CCACFGT, tissue microarray) and nephrogenic adenoma (NA).

RESULTS

33 CCACLUT (24 female, 9 male; mean age 59 years) were collected. CCACLUT most commonly arose from the urinary bladder (26/33, 78%), particularly from the trigone (10/33, 30.3%) followed by the urethra (8/33, 22%). All 12 NA cases were located at the urinary bladder, whereas the most common CCACFGT location was the ovary (29/56, 52%). None of the CCACLUT patients had, intestinal metaplasia, NA, or urothelial carcinoma. One patient had concurrent endometriosis of the sigmoid colon. Most frequently observed morphology in CCACLUT was papillary/tubulocystic (9/3; 27.3%), followed by papillary/tubular (6/33; 18.2%) and papillary/solid (5/33; 15.2%). GATA3 expression was significantly higher in CCACLUT (18/33, 54.5%) and NA (6/12, 50%), when compared to CCACFGT cases 6/56, 11.7%)(p = 0.001 and p = 0.022, respectively). The extent of GATA3 was significantly higher in CCACLUT group (19.2 ± 16.6%) than the other groups (9.6 ± 22.5% in NA and 2.6 ± 9% in CCACFGT group) (p = 0.001). 4/33 patients (12.1) had weak, 10/33 patients (30.3%) had moderate, and 4/33 patients (12.1%) had strong GATA3 intensity in CCACLUT group. In NA group, one patient (8.3%, 1/12) had weak, one patient (8.3%, 1/12) had moderate and 4 patients (33.3%, 4/12) had strong GATA3 intensity. Most cases (CCACLUT 29/33, 88%; NA 11/12, 92%; CCACFGT 46/56, 82.1%) had positive Napsin A expression, by which CCACLUT had significantly more cases with Napsin A expression (p = 0.034). p63 was consistently negative in all cases (30/33 (91.9%) CCACLUT; 12/12 (100%) NA; 42/56 (75%) CCACFGT. Ki67 (MIB) proliferation index was significantly higher in CCACLUT group (54.6 ± 21%) when compared to NA group (4.5 ± 2.7%) and CCACFGT group (35.5 ± 25.8%) (p = 0.001).

CONCLUSION

CCACLUT has consistent GATA3 expression, which may cause challenge in the diagnosis of urothelial carcinoma but can be used to distinguish CCACLUT from CCACFGT.

Association between PAX8AS1 (rs4848320 C > T, rs1110839 G > T, and rs6726151 T > G) and MEG3 (rs7158663) gene polymorphisms and non-Hodgkin lymphoma risk

Long non-coding RNA (lncRNA) PAX8 antisense RNA 1 (PAX8AS1) and Maternal-expressed gene 3 (MEG3) contribute to the pathogenesis of various malignancies including non-Hodgkin lymphoma (NHL). In this study, we aimed to examine the possible association of polymorphisms of PAX8 and MEG3 and the risk NHL. A total of 175 patients and 175 healthy subjects were genotyped by PCR-RFLP and Tetra-Arms PCR assays. Results demonstrated rs4848320 C > T and rs6726151 T > G of PAX8AS1 and rs7158663 of MEG3 play a potential role in the susceptibility of NHL and PAX8AS1 rs1110839 T > G variant was associated with decreased risk of NHL. Haplotype analysis of rs1110839, rs4848320, and rs6726151 demonstrated GCG haplotype is associated with increased risk of lymphoma and TTG, TTT, and GTT haplotypes are related to decreased lymphoma susceptibility.

Molecular Characterization of Muellerian Tumors of the Urinary Tract

In the 2016 WHO classification of genitourinary tumors Muellerian tumors of the urinary tract (MTUT) comprise clear cell adenocarcinomas and endometrioid carcinomas. Since these rare tumors remained understudied, we aimed to characterize their molecular background by performing DNA- and RNA-based targeted panel sequencing. All tumors (n = 11) presented single nucleotide alterations (SNVs), with ARID1A mutations being the most prevalent (5/11, 45%). Besides frequent ARID1A mutations, loss of ARID1A protein is not a suitable marker since protein expression is (partly) preserved also in mutated cases. Copy number alterations (CNVs) were found in 64% of cases (7/11), exclusively gene amplifications. Interestingly, a functionally relevant RSPO2 gene fusion/microdeletion was discovered in the endometrioid adenocarcinoma case. Comparing our findings with mutational profiles of other tumor entities, absence of TERT promoter mutations argues for a non-urothelial origin. No similarities were also found between MTUT and kidney cancers while parallels were observed for specific SNVs with endometrial carcinomas. In conclusion, immunohistochemical PAX8-positivity and lack of TERT promoter mutations could serve as key diagnostic features in difficult cases. Thus, understanding the molecular background of these tumors helps to refine treatment options and offers the possibility of targeted therapies in cases where needed.

Expression of PAX2 and PAX8 in Wilms Tumor: A Tissue Microarray-based Immunohistochemical Study

Background & Objective:

There is currently inadequate information about the expression of immunohistochemical markers in pediatric tumors. Paired box genes 2 and 8 (PAX2 and PAX8) genes have an essential role in kidney organogenesis. This study aimed to investigate the IHC expression of PAX2 and PAX8 in Wilms tumor. Such study would be helpful in diagnosis and possibly in differentiation of this tumor from other mimics, especially in those of poorly differentiated type in small needle biopsy specimens.

Methods:

We performed a cross-sectional study on 45 Wilms tumor cases referred to Bahrami pediatric hospital between 2005 and 2015. Demographic data were collected from medical documents. Sections from related paraffin blocks were provided by the tissue microarray method, and immunohistochemical (IHC) staining was done for PAX8 and PAX2.

Results:

The mean tumor size was 9.98±4.95 cm. Favorable histology was seen in 84.4% of samples. PAX2 was expressed in 41 cases (91.1%), and PAX8 in 37 patients (82.2%). PAX2 and PAX8 expression was mostly seen in both blastemal and epithelial components (77.8% and 66.6%), respectively. Tumors with favorable and unfavorable histology did not significantly differ in PAX2 and PAX8 expression (P=0.637). We found a statically significant relationship between PAX8 expression and tumor size (P=0.033).

Conclusion:

PAX2 and PAX8 markers might helpful in diagnosis of Wilms tumor and may differentiate it from other histologically similar kidney tumors. PAX8 expression may be associated with larger tumor size. Tumors with favorable and unfavorable histology may not be different in PAX2 and PAX8 expression.

Tumour-like lesions of the urinary bladder

There are a number of benign epithelial proliferations in the bladder that may be difficult to distinguish from carcinomas, including urothelial carcinoma and its variants, squamous cell carcinoma and adenocarcinoma. If misdiagnosed, there is the potential for over treatment, with its attendant risk of complications, as well as errors relating to prognostic assessment. In the case of the misdiagnosis of high grade proliferative lesions that mimic invasive carcinoma, unnecessary radical surgery, chemotherapy and radiotherapy may result. Similarly, the misdiagnosis of lesions that have the appearance of low grade carcinoma can prompt a lifetime of radiological investigation and cystoscopies. In this review, we discuss a variety of entities that may be diagnostically challenging and emphasise the importance of identifying key morphological features that have diagnostic utility. We also highlight the importance of relevant clinical information and the clinical settings in which these lesions may occur. In this review we have divided the lesions on the basis of morphology in order to facilitate discussion relating to the differential diagnosis. The architectural patterns we discuss include papillary lesions (polypoid/papillary cystitis and papillary urothelial hyperplasia), pseudocarcinomatous proliferations (pseudocarcinomatous urothelial hyperplasia, florid proliferation of von Brunn nests and fibroepithelial polyps), glandular lesions (intestinal metaplasia and müllerianosis) and lesions with several different patterns (prostatic type urethral polyps and nephrogenic adenoma or metaplasia).

Analysis of PAX8 immunohistochemistry in lung cancers: a meta-analysis

BACKGROUND

In this meta-analysis, we aimed to evaluate the PAX8 immunohistochemical expressions in primary lung cancers and metastatic cancers to the lung.

METHODS

We identified and reviewed relevant articles from the PubMed databases. Ultimately, 18 articles were included in this meta-analysis. PAX8 expression rates were analyzed and compared between primary and metastatic lung cancers.

RESULTS

The PAX8 expression rate in primary lung cancers was 0.042 (95% confidence interval [CI], 0.025 to 0.071). PAX8 expression rates of small cell (0.129; 95% CI, 0.022 to 0.496) and non-small cell carcinomas of the lung (0.037; 95% CI, 0.022 to 0.061) were significantly different (p=.049 in a meta-regression test). However, the PAX8 expression rates of adenocarcinoma (0.013; 95% CI, 0.006 to 0.031) and squamous cell carcinoma (0.040; 95% CI, 0.016 to 0.097) were not significantly different. PAX8 expression rates of metastatic carcinomas to the lung varied, ranging from 1.8% to 94.9%. Metastatic carcinomas from the lung to other organs had a PAX8 expression rate of 6.3%. The PAX8 expression rates of metastatic carcinomas from the female genital organs, kidneys, and thyroid gland to the lung were higher than those of other metastatic carcinomas.

CONCLUSIONS

Primary lung cancers had a low PAX8 expression rate regardless of tumor subtype. However, the PAX8 expression rates of metastatic carcinomas from the female genital organs, kidneys, and thyroid were significantly higher than those of primary lung cancers.

European Association of Urology Guidelines on Primary Urethral Carcinoma-2020 Update

CONTEXT

Primary urethral carcinoma (PUC) is a rare cancer accounting for <1% of all genitourinary malignancies.

OBJECTIVE

To provide updated practical recommendations for the diagnosis and management of PUC.

EVIDENCE ACQUISITION

A systematic search interrogating Ovid (Medline), EMBASE, and the Cochrane Central Register of Controlled Trials and Cochrane Database of Systematic Reviews was performed.

EVIDENCE SYNTHESIS

Urothelial carcinoma of the urethra is the predominant histological type of PUC (54-65%), followed by squamous cell carcinoma (16-22%) and adenocarcinoma (10-16%). Diagnosis of PUC depends on urethrocystoscopy with biopsy and urinary cytology. Pathological staging and grading are based on the tumour, node, metastasis (TNM) classification and the 2016 World Health Organization grading systems. Local tumour extent and regional lymph nodes are assessed by magnetic resonance imaging, and the presence of distant metastases is assessed by computed tomography of the thorax/abdomen and pelvis. For all patients with localised distal tumours (≤T2N0M0), partial urethrectomy or urethra-sparing surgery is a valid treatment option, provided that negative intraoperative surgical margins can be achieved. Prostatic Ta-Tis-T1 PUC can be treated with repeat transurethral resection of the prostate and bacillus Calmette-Guérin. In prostatic or proximal ≥ T2N0 disease, neoadjuvant cisplatin-based chemotherapy should be considered prior to radical surgery. All patients with locally advanced disease (≥T3N0-2M0) should be discussed within a multidisciplinary team. In men with locally advanced squamous cell carcinoma, curative radiotherapy combined with radiosensitising chemotherapy can be offered for definitive treatment and genital preservation. In patients with local urethral recurrence, salvage surgery or radiotherapy can be offered. For patients with distant metastatic disease, systemic therapy based on tumour characteristics can be evaluated.

CONCLUSIONS

These updated European Association of Urology guidelines provide up-to-date guidance for the contemporary diagnosis and management of patients with suspected PUC.

PATIENT SUMMARY

Primary urethral carcinoma (PUC) is a very rare, but aggressive disease. These updated European Association of Urology guidelines provide evidence-based guidance for clinicians treating patients with PUC.

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.

Molecular profiling of clear cell adenocarcinoma of the urinary tract

Clear cell adenocarcinoma (CCA) of the urinary tract is a rare type of malignancy whose molecular profiles remain undefined. Here we reported an integrated clinicopathologic and molecular profiling analysis of four cases of clear cell adenocarcinoma arising in the urethra or the bladder. Utilizing a clinically validated 130-gene exon-sequencing assay, we identified recurrent pathogenic PIK3CA (p. E545K) and KRAS (p.G12D) variants in three of four (75%) of the cases. In addition, an APC variant (P.S2310X), a TP53 variant (p.R273C), and a MYC amplification event were identified. The only CCA case without either PIK3CA or KRAS variants has a distinct pathogenesis through BK virus, demonstrated by positive BK virus PCR and SV40 immunohistochemistry. The novel finding of recurrent variants in the PI3K/AKT/mTOR pathway provides not only insights into oncogenesis but also potential clinical therapeutic targets for patients with clear cell adenocarcinoma of the urinary tract.

Glandular Tumors of the Urachus and Urinary Bladder: A Practical Overview of a Broad Differential Diagnosis

Primary glandular tumors of the urachus and urinary bladder are an intriguing group of clinically and morphologically diverse neoplasms for which there have been recent refinements in diagnostic subclassification and advances in molecular pathology. In addition, the urachus and urinary bladder may be secondarily involved by tumors with glandular differentiation that demonstrate remarkable morphologic, immunophenotypic, and molecular overlap. Thus, surgical pathologists need to be aware of the broad differential diagnosis of glandular tumors that involve the urachus and urinary bladder and have a practical diagnostic framework to evaluate these lesions in routine clinical practice. In this review, we summarize the salient clinical, morphologic, immunohistochemical, and molecular features of glandular tumors of the urachus and urinary bladder, including mucinous cystic tumors of the urachus, noncystic urachal adenocarcinomas, urothelial carcinomas with glandular or pseudoglandular features, primary urinary bladder adenocarcinomas, and Müllerian-type carcinomas, highlighting the strengths and limitations of various diagnostic features and ancillary tests, as well as the need for close clinical and radiographic correlation.

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.

Long non-coding RNA PAX8-AS1 polymorphisms increase the risk of childhood acute lymphoblastic leukemia

The present case-control study was conducted on 110 children with acute lymphoblastic leukemia (ALL) and 120 healthy children to determine the impact of polymorphisms in paired-box gene 8 (PAX8) antisense RNA 1 (PAX8-AS1), namely rs4848320 C>T, rs6726151 T>G and rs1110839 G>T, on ALL risk. Genotyping was performed through the polymerase chain reaction-restriction fragment length polymorphism method. The findings indicated that the rs4848320 variant increased the risk of ALL in codominant [CT vs. CC: odds ratio (OR)=2.13, 95% confidence interval (CI)=1.16-3.90, P=0.014; and TT vs. CC: OR=2.21, 95% CI=1.03-4.74, P=0.041], dominant (CT+TT vs. CC: OR=2.15, 95% CI=1.22-3.81, P=0.009,) and allele (T vs. C: OR=1.55, 95% CI=1.07-2.25, P=0.024) inheritance models. The rs6726151 variant significantly increased the risk of ALL in codominant (GT vs. GG: OR=1.88, 95% CI=1.08-3.27, P=0.036) and overdominant (GT vs. GG+TT: OR=2.08, 95% CI=1.23-3.53, P=0.008) inheritance models. No significant relationship was identified between the rs1110839 G>T variant and disease risk/protection in childhood ALL. In conclusion, the findings of the present study indicated that rs4848320 and rs6726151 polymorphisms of PAX8-AS1 may be a risk factor for the development of childhood ALL. Further studies with larger sample sizes and different ethnicities are now required to confirm these findings.

Nephrogenic Adenoma Complicating Renal Transplantation: A Case Report and Discussion

Nephrogenic adenoma (NA) is a benign adenomatous lesion of the urinary tract. Long considered to be a rare phenomenon, case series from the renal transplant population suggest that it may be much more common within this group. Although NA is considered to be a lesion with low premalignant potential, hematuria, lower urinary tract symptoms, and recurrent urinary tract infections (UTIs) are frequently observed in the context of NA. Furthermore, after resection of NA, lesion recurrence and persistent symptoms are frequently observed. Here we present the case of a 69-year-old male renal transplant recipient with NA and associated recurrent UTIs despite cystoscopic resection of the primary lesion. This case is illustrative of the clinical impact of NA and the need for ongoing work into the development of strategies to manage this problematic phenomenon.

Expression quantitative trait loci for PAX8 contributes to the prognosis of hepatocellular carcinoma

Paired-box family member PAX8 encodes a transcription factor that has a role in cell differentiation and cell growth and may participate in the prognosis of hepatocellular carcinoma (HCC). By bioinformatics analysis, we identified several single nucleotide polymorphisms (SNPs) within a newly identified long non-coding RNA (lncRNA) AC016683.6 as expression quantitative trait loci (eQTLs) for PAX8. Hence, we hypothesized that PAX8eQTLs in lncRNA AC016683.6 may influence the HCC prognosis. We then performed a case-only study to assess the association between the two SNPs as well as the prognosis of HCC in 331 HBV-positive HCC patients without surgical treatment. Cox proportional hazard models were used for survival analysis with adjustments for the age, gender, smoking status, drinking status, Barcelona-Clinic Liver Cancer (BCLC) stage, and chemotherapy or TACE (transcatheter hepatic arterial chemoembolization) status. We found that the G allele of rs1110839 and the T allele of rs4848320 in PAX8was significantly associated with a better prognosis compared with the T allele of rs1110839 and the C allele of rs4848320 (adjusted HR = 0.74, 95% CI = 0.61–0.91, P = 0.004 for rs1110839 and adjusted HR = 0.71, 95% CI = 0.54–0.94, P = 0.015 for rs4848320 in the additive model). Furthermore, the combined effect of the variant genotypes for these two SNPs was more prominent in patients with the BCLC-C stage orpatients with chemotherapy or TACE. Although the exact biological function remains to be explored, our findings suggest a possible association of PAX8eQTLs in lncRNA AC016683.6 with the HCC prognosis inthe Chinese population. Further large and functional studies are needed to confirm our findings.

Clear Cell Adenocarcinoma of the Urethra in Women: Distinctive MRI Findings for Differentiation From Nonadenocarcinoma and Non-Clear Cell Adenocarcinoma of the Urethra

OBJECTIVE

The purpose of this study is to evaluate the MRI findings differentiating clear cell adenocarcinoma of the urethra (CCAU) from nonadenocarcinoma of the urethra (NACU) and non-clear cell adenocarcinoma of the urethra (NCCAU) in women.

MATERIALS AND METHODS

Six women with pathologically proven CCAU, six women with pathologically confirmed NACU (two squamous cell carcinomas and four transitional cell carcinomas), and nine women with NCCAU underwent preoperative MRI. The MRI findings for CCAU, NACU, and NCCAU were reviewed by a radiologist who was blinded to the histopathologic findings and were compared using the Mann-Whitney U test and the Fisher exact test.

RESULTS

CCAU was shorter in height than NACU (3.4 cm vs 5.5 cm; p = 0.020) and also had a smaller height-to-width ratio than NACU (0.85 vs 1.51; p < 0.001) and NCCAU (0.85 vs 1.48; p = 0.002). The proportion of preserved urethra in CCAU (67%) was larger than that in either NACU (9%; p < 0.001) or NCCAU (22%; p < 0.001). All cases of CCAU originated within a diverticulum, whereas none of the cases of NACU and only one NCCAU originated in a diverticulum. Intratumoral septation was more frequently observed in CCAU (100%) than in NACU (16.6%; p = 0.015) or NCCAU (11.1%; p = 0.001).

CONCLUSION

MRI findings for CCAU were significantly distinctive, compared with findings for NACU and NCCAU. All cases of CCAU were associated with a urethral diverticulum, and CCAU had a lower height-to-width ratio, more frequent intratumoral septation, and greater preservation of normal urethra than did NACU and NCCAU.

Clear Cell Urothelial Carcinoma

Clear cell urothelial carcinoma (CCUC) is a rare variant of urothelial carcinoma (UC) and its clinical significance has not been well elucidated. Consecutive cases of UC over a period of 5 years were reviewed. Histopathological tumor parameters, including the proportion of tumor cells with clear cell change, and patient outcomes were recorded. Expression of the following immunohistochemical markers was investigated: CK7, CK20, CK5, CD44, and PAX8. We also conducted a review of the literature for case reports/series of CCUC. Ten CCUCs were identified out of a total of 872 cases of UC. The clear cell component was characterized by prominent cytoplasmic membranes and voluminous clear cytoplasm, and accounted for 30% to 90% of the invasive tumor component. Of all the non-CCUC cases reviewed, at least 50% (noninvasive or invasive UC) showed focal areas of clear cell change that accounted for less than 5% of the neoplastic cells. Immunohistochemically, CCUC exhibited positive reactivity for CK5/CD44 (n = 9); CK20 (n = 5), PAX8 (very focal to extensive) (n = 6), and GATA3/CK7 (n = 10). Eight of 10 CCUC were of advanced clinical stage (pT3/pT4) and 6 of 10 experienced tumor recurrence and/or death due to disease. In conclusion, CCUC can be distinguished from non-CCUC by the extensive clear cell change in more than 30% of cells. This variant is associated with rapid progression to muscle invasion and metastasis, with an aggressive clinical course. Expression of CK5/CD44 may represent basal cell features in most CCUC cases, while PAX8 expression is suggestive of mesonephric derivation.

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.

Updates in Benign Lesions of the Genitourinary Tract

The genitourinary tract is a common site for new cancer diagnosis, particularly for men. Therefore, cancer-containing specimens are very common in surgical pathology practice. However, many benign neoplasms and nonneoplastic, reactive, and inflammatory processes in the genitourinary tract may mimic or cause differential diagnostic challenges with malignancies. Emerging clinicopathologic, immunohistochemical, and molecular characteristics have shed light on the pathogenesis and differential diagnosis of these lesions. This review addresses differential diagnostic challenges related to benign genitourinary tract lesions in the kidney, urinary bladder, prostate, and testis, with emphasis on recent advances in knowledge and areas most common in diagnostic practice.

Diffuse and multifocal nephrogenic adenoma with Familial Mediterranean Fever: a case report with molecular study

Nephrogenic adenoma, also referred to nephrogenic metaplasia, is a benign proliferative lesion of urothelium, usually associated with chronic physical stimuli or inflammation. Familial Mediterranean fever is an inherited autosomal recessive disease characterized by recurrent short episodes of fever. The site of mutation is found in MEFV gene which controls inflammatory responses. We have experienced a case of nephrogenic adenoma in a 16-year-old girl with Familial Mediterranean Fever, showing proliferative lesions diffusely in the urinary bladder and multifocally in the other parts of urinary tract. These lesions disappeared after colchicine treatment. We searched for MEFV gene mutation using the specimen from the resected urinary bladder and detected heterozygous mutation of E148Q. There is a possibility that control of inflammation caused by the surgery for vesicoureteral reflux in the local site didn’t work well on the background of heterozygous mutation of MEFV gene, and as a result, nephrogenic adenoma appeared. This is the first report of a combination of two rare diseases. We have to be aware that nephrogenic adenoma can occur in association with Familial Mediterranean Fever, and the former condition should be taken into consideration when rendering a correct pathological diagnosis.

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

Glandular lesions of the urinary bladder include a broad spectrum of entities ranging from completely benign to primary and secondary malignancies. The accurate diagnosis of these lesions is both important and challenging. Recently, studies suggest that telomerase reverse transcriptase (TERT) promoter mutations could be a biomarker for urothelial carcinoma (UC). We hypothesized that these mutations can distinguish UC with glandular differentiation from nephrogenic adenoma, primary adenocarcinoma of the urinary bladder (PAUB), or secondary malignancies. Twenty-five cases of benign glandular lesions (including nephrogenic adenoma); 29 cases of UC with glandular differentiation; 10 cases of PAUB; and 10 cases each of metastatic colon cancer, prostatic carcinoma, and carcinoma from Mullerian origin were collected. Slides were reviewed and selected to make sure the lesion was at least 10% to 20% of all tissue. Macrodissection was performed in some of cases, and genomic DNA was extracted from the tissue. Telomerase reverse transcriptase promoter mutations were determined by standard polymerase chain reaction sequencing. Twenty-one cases (72%) of UC with glandular differentiation were positive for TERT promoter mutations. However, none of the remaining cases (total 65 cases of benign lesions, PAUB, and metastatic carcinomas) was positive for TERT promoter mutation. Telomerase reverse transcriptase promoter mutations were highly associated with UC including UC with glandular differentiation but not other glandular lesions of bladder. Therefore, in conjunction with morphologic features, Immunohistochemistry stain profile, and clinical information, TERT promoter mutations could distinguish UC with glandular differentiation from other bladder glandular lesions. In addition, lack of TERT promoter mutations in primary adenocarcinoma of bladder suggests that this entity may have different origin or carcinogenesis from those of UC.

Neuropilin-2 Is a Newly Identified Target of PAX8 in Thyroid Cells

PAX8 is a transcription factor essential for thyroid gland development, as well as for the maintenance of the thyroid differentiated state in the adult. In particular, PAX8 has been comprehensively shown to regulate genes that are considered markers of thyroid differentiation. However, a better knowledge of genes transcriptionally regulated by PAX8 is desirable to clarify its role in endocrine syndromes and cancer susceptibility. In order to further investigate PAX8 downstream targets, we recently performed a genome-wide expression analysis following PAX8 knockdown in FRTL-5 thyroid cells and Neuropilin-2 was identified as a potential transcriptional target of PAX8. In this study, we determined the role of the transcription factor PAX8 in the regulation of Neuropilin-2 expression. Indeed, in thyroid cells PAX8 directly binds the Neuropilin-2 promoter leading to its transcriptional repression. Interestingly, we observed an inverse correlation between the expression of PAX8 and Neuropilin-2 in thyroid carcinoma tissues and cell lines compared to non-tumor counterparts, suggesting a critical role of PAX8 in regulating Neuropilin-2 expression in vivo. Notably, ectopic overexpression of PAX8 in FB-2 thyroid cancer cells promotes Neuropilin-2 downregulation producing a significant reduction in cell proliferation, migration ability, and invasion activity and reverting the cell phenotype from mesenchymal to a more epithelial one. These findings uncover the novel interplay between PAX8 and Neuropilin-2, which is likely to be important in the pathogenesis of thyroid diseases.

Nephrogenic Adenoma of the Urinary Bladder: A Review of the Literature

Background. Nephrogenic adenoma of the urinary bladder (NAUB) is a rare lesion associated with nonspecific symptoms and could inadvertently be misdiagnosed. Aim. To review the literature. Methods. Various internet search engines were used. Results. NAUB is a benign tubular and papillary lesion of the bladder, is more common in men and adults, and has been associated with chronic inflammation/irritation, previous bladder surgery, diverticula, renal transplantation, and intravesical BCG; recurrences and malignant transformations have been reported. Differential diagnoses include clear cell adenocarcinoma, endocervicosis, papillary urothelial carcinoma, prostatic adenocarcinoma of bladder, and nested variant of urothelial carcinoma; most NAUBs have both surface papillary and submucosal tubular components; both the papillae and tubules tend to be lined by a single layer of mitotically inactive bland cells which have pale to clear cytoplasm. Diagnosis may be established by using immunohistochemistry (positive staining with racemase; PAX2; keratins stain positive with fibromyxoid variant), electron microscopy, DNA analysis, and cytological studies. Treatment. Endoscopic resection is the treatment but recurrences including sporadic malignant transformation have been reported. Conclusions. There is no consensus on best treatment. A multicentre study is required to identify the treatment that would reduce the recurrence rate, taking into consideration that intravesical BCG is associated with NAUB.

Application of Immunohistochemistry in Thyroid Pathology

Context

Accurate classification of follicular-patterned thyroid lesions is not always an easy task on routine surgical hematoxylin-eosin–stained or cytologic fine-needle aspiration specimens. The diagnostic challenges are partially due to differential diagnostic criteria that are often subtle and subjective. In the past decades, tremendous advances have been made in molecular gene profiling of tumors and diagnostic immunohistochemistry, aiding in diagnostic accuracy and proper patient management.

Objective

To evaluate the diagnostic utility of the most commonly studied immunomarkers in the field of thyroid pathology by review of the literature, using the database of indexed articles in PubMed (US National Library of Medicine) from 1976–2013.

Data Sources

Literature review, authors' research data, and personal practice experience.

Conclusions

The appropriate use of immunohistochemistry by applying a panel of immunomarkers and using a standardized technical and interpretational method may complement the morphologic assessment and aid in the accurate classification of difficult thyroid lesions.

The Application of Immunohistochemical Biomarkers in Urologic Surgical Pathology

Context

Tumors of the genitourinary tract can be diagnostically challenging, particularly in core biopsies and cystoscopic biopsies with limited material. Immunohistochemistry is a valuable tool to use when morphology alone is insufficient for diagnosis.

Objectives

To review tumors and benign lesions of the kidney, urinary bladder, prostate gland, testis, and paratesticular structures with an emphasis on difficult differential diagnoses, as well as staining patterns in normal tissue. Recommended immunohistochemical stain panels are discussed that can assist in the diagnostic workup.

Data Sources

Review of current literature.

Conclusions

Immunohistochemistry is a valuable tool, assisting in the diagnosis of problematic tumors and benign lesions of the genitourinary tract.

t(6;11) renal cell carcinoma (RCC): expanded immunohistochemical profile emphasizing novel RCC markers and report of 10 new genetically confirmed cases

Renal cell carcinomas (RCCs) harboring the t(6;11)(p21;q12) translocation were first described in 2001 and recently recognized by the 2013 International Society of Urological Pathology Vancouver Classification of Renal Neoplasia. Although these RCCs are known to label for melanocytic markers HMB45 and Melan A and the cysteine protease cathepsin K by immunohistochemistry (IHC), a comprehensive IHC profile has not been reported. We report 10 new t(6;11) RCCs, all confirmed by break-apart TFEB fluorescence in situ hybridization. A tissue microarray containing 6 of these cases and 7 other previously reported t(6;11) RCCs was constructed and immunolabeled for 21 different antigens. Additional whole sections of t(6;11) RCC were labeled with selected IHC markers. t(6;11) RCC labeled diffusely and consistently for cathepsin K and Melan A (13 of 13 cases) and almost always at least focally for HMB45 (12 of 13 cases). They labeled frequently for PAX8 (14 of 23 cases), CD117 (10 of 14 cases), and vimentin (9 of 13 cases). A majority of cases labeled at least focally for cytokeratin Cam5.2 (8 of 13 cases) and CD10 and RCC marker antigen (10 of 14 cases each). In contrast to a prior study's findings, only a minority of cases labeled for Ksp-cadherin (3 of 19 cases). The median H score (product of intensity score and percentage labeling) for phosphorylated S6, a marker of mTOR pathway activation, was 101, which is high relative to most other RCC subtypes. In summary, IHC labeling for PAX8, Cam5.2, CD10, and RCC marker antigen supports classification of the t(6;11) RCC as carcinomas despite frequent negativity for broad-spectrum cytokeratins and EMA. Labeling for PAX8 distinguishes the t(6;11) RCC from epithelioid angiomyolipoma, which otherwise shares a similar immunoprofile. CD117 labeling is more frequent in the t(6;11) RCC compared with the related Xp11 translocation RCC. Increased pS6 expression suggests a possible molecular target for the uncommon t(6;11) RCCs that metastasize.

Primary urethral clear-cell adenocarcinoma: comprehensive analysis by surgical pathology, cytopathology, and next-generation sequencing

Primary clear-cell adenocarcinoma of the urethra, a rare tumor that histomorphologically resembles clear-cell carcinoma of the female genital tract, occurs predominantly in women and is associated with a relatively poor prognosis. The histogenesis of this rare urethral neoplasm has not been completely resolved, but it is thought to arise from either müllerian rests or metaplastic urothelium. Herein, we present comprehensive surgical pathological and cytopathological findings from a patient with primary urethral clear-cell adenocarcinoma and describe next-generation sequencing results for this patient's unique tumor-the first such reported characterization of molecular aberrations in urethral clear-cell adenocarcinoma at the transcriptomic and genomic levels. Transcriptome analysis revealed novel gene fusion candidates, including ANKRD28-FNDC3B. Whole-exome analysis demonstrated focal copy number loss at the SMAD4 and ARID2 loci and 38 somatic mutations, including a truncating mutation in ATM and a novel nonsynonymous mutation in ALK.

Newly Available Antibodies With Practical Applications in Surgical Pathology

Selected antibodies that have become available in recent years and have applications in diagnostic pathology are discussed. They include antibodies that are organ-related, provide information on cellular differentiation or histogenetic type, have predictive value in tumors, and highlight infective agents. PAX8 (paired box gene 8) is a marker expressed in the lower female genital tract, thyroid, and kidney and their tumors. Napsin A is expressed in the lung and kidney and is an alternative marker for pulmonary adenocarcinoma. Arginase A is a sensitive and specific marker for liver tumors. ERG (Ets-related gene) is an excellent marker for endothelium and vascular tumors as well as prostatic cancer (about 50% of cases). SOX10 (SRY-related HMG box) is expressed predominantly in melanocytic and Schwann cells and the corresponding tumors. DOG1 (discovered on GIST 1) is an excellent marker for gastrointestinal stromal tumor (GIST) and acinic cell carcinoma. OCT3/4 is a pan–germ cell tumor marker, except yolk sac tumor. SALL4 is positive in various types of germ cell tumors, including yolk sac tumor. MUC4 (mucin-related antigen 4) is a sensitive and specific marker for low-grade fibromyxoid sarcoma. Langerin is a specific marker for Langerhans cells and their tumors. SOX11 is a sensitive marker for mantle cell lymphoma. New generation antibodies against anaplastic lymphoma kinase (ALK) are required to reliably demonstrate ALK gene translocation in pulmonary carcinomas. Lack of expression of succinate dehydrogenase B is seen in paragangliomas of the hereditary form and in the pediatric type of GIST. Antibodies against Trepenoma pallidum can facilitate the diagnosis of syphilis, whereas those against SV40 (simian virus 40) are helpful for diagnosis of BK virus infection and progressive multifocal leukoencephalopathy.

Nephrogenic adenoma of the urinary tract: clinical, histological, and immunohistochemical characteristics

Nephrogenic adenoma is a benign condition of the urinary tract resulting from the displacement and seeding of renal tubular cells from the renal pelvis to the urethra. A retrospective series of 134 cases collected from four hospitals in three different countries was analyzed in this study. Recorded clinical data included age and sex, topography, urological antecedents, coexistent lesions, and follow-up. Cytonuclear and architectural features were reviewed, and PAX-8, p63, PSMA, S100A1, CEA, EMA, CD117, cannabinoid receptor CB1, AMACR, E-cadherin, and CD10 antibodies were included in an immunohistochemical panel. Males predominated (105 M/29 F) with an average age of 66 years (range, 14-96). Urothelial carcinoma was the most frequent clinical antecedent (43.2 %) and also the most common coexisting lesion (14 %). Tubular architecture was the most frequent pattern detected (40 %) although most cases showed a mixed pattern (45.5 %). Deep infiltrative growth into the muscularis propria occurred in two cases. EMA and PAX-8 were expressed in 100 % of nephrogenic adenomas, while E-cadherin reactivity was observed in 66.6 % of cases, cannabinoid receptor CB1 in 25 %, CD10 in 13.6 %, CD117 in 4.1 %, and AMACR in 2.7 %. For the rest of the antigens, no reactivity was found. The average time lapse between the pathological antecedent and the discovery of a nephrogenic adenoma was 32 months. We conclude that nephrogenic adenoma displays a broad spectrum of histological features that may mimic malignancy. In our experience, CB1 immunostaining adds a further argument in favor of a renal origin of this lesion. The combination of PAX-8+, p63-, and EMA + distinguishes nephrogenic adenoma from urothelial and prostate carcinoma, its most frequent malignant look-alikes.

Pax8 has a critical role in epithelial cell survival and proliferation

The transcription factor Pax8, a member of the Paired-box gene family, is a critical regulator required for proper development and differentiation of thyroid follicular cells. Despite being Pax8 well characterized with respect to its role in regulating genes responsible for thyroid differentiation, its involvement in cell survival and proliferation has been hypothesized but remains unclear. Here, we show that Pax8 overexpression significantly increases proliferation and colony-forming efficiency of Fischer rat thyroid line 5 epithelial cells, although it is not sufficient to overcome their hormone dependence. More interestingly, we show that Pax8-specific silencing induces apoptosis through a p53-dependent pathway that involves caspase-3 activation and cleavage of poly(ADP)ribose polymerase. Our data indicate that tumor protein 53 induced nuclear protein 1 (tp53inp1), a positive regulator of p53-dependent cell cycle arrest and apoptosis, is a transcriptional target of Pax8 and is upregulated by Pax8 knockdown. Remarkably, tp53inp1 silencing significantly abolishes Pax8-induced apoptosis thus suggesting that tp53inp1 may be the mediator of the observed effects. In conclusion, our data highlight that Pax8 is required for the survival of differentiated epithelial cells and its expression levels are able to modulate the proliferation rate of such cells.

Flat pattern of nephrogenic adenoma: previously unrecognized pattern unveiled using PAX2 and PAX8 immunohistochemistry

Nephrogenic adenoma is a benign lesion of the urinary tract, particularly the urinary bladder. It is a gross and microscopic mimicker of urothelial neoplasm or metastatic carcinoma. Several histological patterns (tubular, tubulocystic, polypoid, papillary, fibromyxoid) have been recognized, but a flat pattern has not been described. Histologically, nephrogenic adenoma consists of tubules, cysts or papillae lined by flat to polygonal cells with frequent hobnail appearance. The stroma is often edematous or has a granulation tissue-like appearance with acute or chronic inflammation. By immunohistochemistry, nephrogenic adenomas are positive for renal epithelial markers CK7, CD10 and alpha-methylacyl-coenzyme A racemase, and negative for bladder urothelium or prostate markers. Recent studies have shown that nephrogenic adenomas are positive for PAX2 and PAX8. We encountered an interesting case of tubular nephrogenic adenoma with adjacent areas suspicious of flat urothelial atypia. Immunohistochemistry for PAX2 and PAX8 were positive in these areas, unveiling a flat pattern of nephrogenic adenoma. This case prompted us to study 15 cases of nephrogenic adenoma to determine additional instances of flat pattern and to assess the value of PAX2 and PAX8 immunoreactivity to diagnose nephrogenic adenoma. PAX2 and PAX8 immunostaining was positive in 14/15 and 15/15 cases, respectively. The flat pattern was present at least focally adjacent to tubular, polypoid and papillary areas, in 8/15 cases of nephrogenic adenoma. In conclusion, the flat pattern is a common finding in nephrogenic adenomas, but easily under recognized by morphologic examination and may be confused with flat urothelial lesions with atypia. Immunostains for PAX2 and PAX8 are useful in the detection of nephrogenic adenomas and particularly unveil those nephrogenic adenomas with flat pattern.

Nephrogenic adenomas in pediatric patients: a morphologic and immunohistochemical study of 21 cases

Similar to nephrogenic adenomas in adults, those in children are rare benign lesions that often occur in the setting of previous surgery or chronic irritation of the urinary tract. These lesions often present with hematuria and/or as polypoid or papillary lesions on cystoscopy, which may indicate malignancy. We sought to evaluate the various patterns of nephrogenic adenoma occurring in the pediatric population and better characterize the immunophenotype of these lesions. We reviewed 21 cases of nephrogenic adenomas from urinary bladder biopsies of 16 patients. Most patients had a history of urinary bladder augmentation with recurrent urinary stones and urinary tract infections. Many cases presented as a papillary or polypoid mass on cystoscopy. The most common morphologic patterns are papillary, tubulocystic, and a mixed pattern of papillary and tubulocystic, followed by cystic and tubular. On immunostaining, PAX-2, PAX-8, CK7, and MUC-1 provided the most diffuse and intense positive reactivity for nephrogenic adenoma, whereas CD10 and P504S were focal and lesser in intensity when positive. p63 and PAX-5 were consistently negative. We conclude that, although rare in children, nephrogenic adenoma should be included in the differential diagnosis of papillary/polypoid lesions in the urinary tract, especially in the context of previous surgery, chronic irritation from recurrent urinary tract infections, or stones. The immunohistochemistry profile of nephrogenic adenomas in our study also provides evidence that these are derived from distal renal tubular cells. In difficult cases, an immunohistochemical panel consisting of cytokeratin 7, PAX-2, PAX-8, and MUC-1 may be useful.