PAX8 (+)/p63 (-) immunostaining pattern in renal collecting duct carcinoma (CDC): a useful immunoprofile in the differential diagnosis of CDC versus urothelial carcinoma of upper urinary tract

Italian Registry on Rare Urological Tumors (Meet-URO-23): The First Analysis on Collecting Duct Carcinoma of the Kidney

INTRODUCTION

Rare genitourinary tumors are lacking of randomized and observational data. We aimed to describe the clinical characteristics and outcomes of patients with collecting duct carcinoma (CDC) through the Meet-URO 23/I-RARE database.

MATERIALS AND METHODS

We performed a multicentric retrospective-prospective study within the Meet-URO network, enrolling patients from March 2021 (retrospectively up from 2011) until March 2023. The primary objective was to describe the clinical characteristics of patients with CDC, the secondary objectives were to assess the oncological outcomes in terms of relapse-free survival (RFS), progression-free survival (PFS), overall survival (OS) and objective response rate (ORR) to treatment.

RESULTS

37 patients with CDC were enrolled. Four patients underwent only surgery, 33 received first-line systemic therapy. Median OS was 22.1 months (95% CI, 8.9-31.9). Median RFS for patients with localized disease at onset (n = 30) was 3.7 months (95% CI, 1.9-12.8), median PFS for first-line treatment was 3.3 months (95% CI, 2.7-9.9), with an ORR of 27%. Female sex and good performance status (PS) were associated with longer PFS (P = .072 and P < .01, respectively) and OS (P = .030 and P = .141, respectively).

CONCLUSIONS

Patients with CDC had dismal prognosis, with scarce benefit from the available treatments. Female sex and good PS seemed to be associated with better prognosis.

A Rare Case of Collecting Duct Carcinoma With Extensive Coagulative Necrosis

Collecting duct carcinoma (CDC) is an aggressive renal malignancy with limited diagnostic and therapeutic consensus. We report a case of a 69-year-old male with CDC and extensive coagulative necrosis who presented with lower extremity swelling, abdominal distention, and an enlarged left kidney causing grade IV hydronephrosis. Initial treatment with a left percutaneous nephrostomy was followed by clinical deterioration and a diagnosis of emphysematous pyelonephritis. Pathological examination of drainage material revealed extensive coagulative necrosis and was suggestive of a necrotic neoplasm. Subsequent left nephrectomy confirmed CDC with high-grade features, stromal desmoplasia, and extensive coagulative necrosis. Immunohistochemistry studies supported the diagnosis. This study highlights the diagnostic complexity of CDC and emphasizes the need for accurate reporting of atypical presentations. CDC remains a formidable clinical entity with limited treatment options and poor outcomes. Further research is essential to enhance our understanding and management of this rare and aggressive renal malignancy.

Identifying SOX17 as a Sensitive and Specific Marker for Ovarian and Endometrial Carcinomas

Similar to PAX8, SOX17 was recently identified as a master transcription factor of ovarian cancer based on RNA sequencing data. We explored SOX17 utility in diagnosing ovarian tumors and other gynecologic tumors. We systematically evaluated SOX17 expression on tissue microarrays of 398 ovarian tumors of various types, 93 endometrial carcinomas, 80 cervical carcinomas, and 1371 nongynecologic carcinomas, such as those of kidney, thyroid, breast, colon, bladder, liver, bile duct, adrenal gland, pancreas, brain, and lung and malignant melanoma. In addition, we evaluated SOX17 expression in whole tissue sections from 60 gynecologic carcinomas and 10 angiosarcomas. The results demonstrated that SOX17 was highly expressed in most ovarian and endometrial tumors with strong intensity. However, unlike PAX8, it was predominately negative in other tested tumor types, including kidney and thyroid tumors. In particular, SOX17 was highly expressed in the following pathologic subtypes of ovarian tumors: serous carcinoma, clear cell carcinoma, endometrioid carcinoma, and germ cell tumors. SOX17 was mostly negative in mucinous carcinoma and sex cord stromal tumors. In addition, SOX17 was expressed in vascular endothelial cells and was positive in all tested angiosarcomas. In summary, our results demonstrate that SOX17 is a sensitive and specific marker for ovarian nonmucinous carcinomas and endometrial carcinomas. For ovarian germ cell tumors and angiosarcomas, SOX17 demonstrates higher specificity than PAX8, with comparable sensitivity. Furthermore, SOX17 positivity in endothelial cells serves as an internal positive control, making it an excellent marker.

"Collecting duct carcinoma of the kidney: diagnosis and implications for management"

Collecting duct carcinoma of the kidney is a rare and aggressive subtype of renal cell carcinoma (RCC) arising from the distal convoluted tubules. At the time of diagnosis, patients are more frequently symptomatic, with advanced locoregional stage, and have metastatic disease. The 2016 WHO Classification of Tumours of the Urinary System defined diagnostic criteria for this entity. However, the diagnostic features continue to evolve, with typical, but not entirely specific, histologic and immunophenotypic characteristics. In addition, the lack of consistent molecular alterations makes collecting duct carcinoma a diagnosis of exclusion, with historical cases being re-classified as fumarate hydratase deficient RCC, ALK rearranged RCC, renal medullary carcinoma or high-grade urothelial carcinoma. The rarity and poor prognosis of the tumor makes it difficult to reach consensus guidelines to guide therapy. In this manuscript we review the clinicopathologic features of collecting duct carcinoma including pathologic diagnostic criteria, molecular characteristics and differential diagnosis, and their possible implications for management.

Contemporary Clinical Definitions, Differential Diagnosis, and Novel Predictive Tools for Renal Cell Carcinoma

Despite significant progress regarding clinical detection/imaging evaluation modalities and genetic/molecular characterization of pathogenesis, advanced renal cell carcinoma (RCC) remains an incurable disease and overall RCC mortality has been steadily rising for decades. Concomitantly, clinical definitions have been greatly nuanced and refined. RCCs are currently viewed as a heterogeneous series of cancers, with the same anatomical origin, but fundamentally different metabolisms and clinical behaviors. Thus, RCC pathological diagnosis/subtyping guidelines have become increasingly intricate and cumbersome, routinely requiring ancillary studies, mainly immunohistochemistry. Meanwhile, RCC-associated-antigen targeted systemic therapy has been greatly diversified and emerging, novel clinical applications for RCC immunotherapy have already reported significant survival benefits, at least in the adjuvant setting. Even so, systemically disseminated RCCs still associate very poor clinical outcomes, with currently available therapeutic modalities only being able to prolong survival. In lack of a definitive cure for advanced RCCs, integration of the amounting scientific knowledge regarding RCC pathogenesis into RCC clinical management has been paramount for improving patient outcomes. The current review aims to offer an integrative perspective regarding contemporary RCC clinical definitions, proper RCC clinical work-up at initial diagnosis (semiology and multimodal imaging), RCC pathological evaluation, differential diagnosis/subtyping protocols, and novel clinical tools for RCC screening, risk stratification and therapeutic response prediction.

NUTM1-fusion positive malignant neoplasms of the genitourinary tract: A report of six cases highlighting involvement of unusual anatomic locations and histologic heterogeneity

Tumors with NUTM1 fusions occur predominantly in the thoracic cavity and head and neck region. However, recent literature expanded the location of NUTM1-translocated malignancy to soft tissue, brain, and visceral organs. In this study, we describe the first series of six NUTM1-translocated carcinomas and sarcomas occurring in the genitourinary tract. The sites of origin were kidney (n = 2), bladder (n = 3), and penis (n = 1). All tumors occurred in adulthood (range: 30-78 years). The histologic features were heterogeneous, showing epithelial, spindle cell, or primitive small blue round cell morphology. Glandular architecture, keratinization, rhabdoid cells, or myxoid-to-edematous stromal component were also noted. In three cases, features were in keeping with a carcinoma (two from kidney and one from bladder), whereas the remaining three were classified as malignant undifferentiated neoplasm (MUN)/sarcoma. Fusion partners detected in four cases tested by either FISH and/or RNA sequencing were BRD4 in two kidney tumors, MXD1 in a bladder sarcoma, and MXD4 in a penile sarcoma. NUT immunostain showed diffuse spiculated positivity in five cases. Immunopositivity for various cytokeratins was noted in two tumors. The outcome of NUTM1-rearranged genitourinary malignancy was dismal: four of five cases with follow-up developed distant metastasis, and three suffered disease-specific death. In conclusion, NUTM1-rearranged carcinoma and sarcoma can affect the genitourinary tract, including kidney, bladder, and penis. Histologic features and keratin immunoexpression are highly variable. A NUTM1-fusion positive malignancy may be included in the differential diagnosis of a MUN of the genitourinary tract given the dismal outcome and the existing BET-targeted therapy for tumors with BRD3/4::NUTM1 fusion.

A genomic mutation spectrum of collecting duct carcinoma in the Chinese population

BACKGROUND

Renal collecting duct carcinoma (CDC) is a rare and lethal subtype of renal cell carcinoma (RCC). The genomic profile of the Chinese population with CDC remains unclear. In addition, clinical treatments are contradictory. In this study, we aimed to identify the genomic mutation spectrum of CDC in the Chinese population.

METHODS

Whole-exome sequencing was performed using the Illumina Novaseq™ 6000 platform. MuTect2 detects single-nucleotide variants (SNVs) and small scale insertions/deletions (INDELs). The identified mutations were annotated with ANNOVAR and validated by Sanger sequencing. Control-FREEC was used to detect copy number variation (CNV), and GISTIC was applied to detect frequently mutated altered regions. These data were compared with associated The Cancer Genome Atlas cohorts.

RESULTS

Ten normal-matched CDC patients were included. The mean tumour mutation burden was 1.37 Mut/Mb. Six new recurrent somatic mutated genes were identified, including RBM14, MTUS1, GAK, DST, RNF213 and XIRP2 (20% and 2 of 10, respectively), and validated by Sanger sequencing. In terms of common mutated genes, SETD2 was altered in both CDC and other RCC subtypes but not in bladder urothelial carcinoma (BLCA); CDKN2A was a driver gene in both CDC (SNV: 10%, 1 of 10) and BLCA but not in other RCC subtypes. Next, 29 amplifications and 6 deletions of recurrent focal somatic CNVs were identified by GISTIC2.0, which displayed differences from kidney renal clear cell carcinoma (KIRC), kidney renal papillary cell carcinoma (KIRP) and BLCA cohorts. Of note, CDKN2A (CNV alteration: 30%, 3 of 10) and CDKN2A-AS1 were the only overlapping genes of these four cohorts. Importantly, the CDKN2A mutation in our cohort differed from previous studies in urinary carcinomas. Moreover, CDKN2A-altered cases had significantly worse overall survival than wild-type cases in both KIRC and KIRP cohorts. In addition, the most frequently altered genomic pathway of our CDC cohort was the CDKN2A-mediated p53/RB1 pathway.

CONCLUSIONS

Our study offers the first genomic spectrum of the Chinese population with CDC, which differs from that of the Western population. The altered CDKN2A-mediated p53/RB1 pathway might provide new insight into potential therapeutic targets for CDC patients.

Immunohistochemistry for the diagnosis of renal epithelial neoplasms

Despite the increasing number of newly identified renal neoplasms, the diagnosis of renal cell carcinoma (RCC) can usually be reached with careful histologic examination and a limited immunohistochemical (IHC) panel. Clear cell, papillary, chromophobe RCC and oncocytoma account for more than 90% of renal neoplasia in adults, and sophisticated ancillary tools are usually unnecessary. Renal tumors with entity-defining genetic alterations may ultimately require molecular confirmation via cytogenetics or sequencing technologies, such as RCC with TFE3, TFEB, or ALK gene rearrangements, or TFEB amplified RCC. In fumarate hydratase-deficient and succinate dehydrogenase-deficient RCC, highly specific IHC markers can strongly suggest the diagnosis. In the metastatic setting, PAX8 and carbonic anhydrase 9 are among the most helpful markers for confirming RCC and clear cell type, respectively; however, caution should be exercised in the absence of a current or historical renal mass. In diagnostically challenging cases, such as renal eosinophilic tumors with low-grade nuclear features, or infiltrative high-grade tumors, careful examination coupled with a judicious panel of IHC markers usually resolves the diagnosis. This review offers concise algorithms for diagnosis of kidney neoplasia with the latest recognized, provisional, and emerging entities to daily pathology practice.

Incidence, Clinical Characteristics, and Survival of Collecting Duct Carcinoma of the Kidney: A Population-Based Study

Objective

To investigate the exact age‐adjusted incidence (AAI), clinical characteristics, and survival data of collecting duct carcinoma of the kidney (CDCK) recorded in the Surveillance, Epidemiology, and End Results (SEER) database of the National Cancer Institute.

Methods

Patients with CDCK confirmed by microscopic examination from 2004 to 2018 were selected from the SEER database. AAI rates were calculated using SEER*Stat software (version 8.3.9). The Kaplan‐Meier method was used to evaluate cancer-specific survival (CSS) rates according to tumor size, tumor stage, and treatment methods, and differences among these variables were assessed by the log‐rank test. Cox regression analysis was employed to identify variables independently related to CSS.

Results

A total of 286 patients with CDCK were identified from the database. The majority of the patients were white (69.2%), male (67.5%), and married (60.5%), and the median age was 59 years. Most patients with CDCK (74.4%) presented with stages III or IV disease. The diameter of most (59.4%) tumors was less than 7 cm, and the tumors were more commonly found on the left than on the right (55.2% vs. 44.8%). The incidence of CDCK decreased over time. The median CSS time was 17 months. In terms of the treatment modalities used, 83.9% of the patients underwent surgery; 32.9% underwent chemotherapy, and 13.6% underwent radiotherapy. The CSS rates at 1, 2, and 5 years were 57.3%, 43.2%, and 30.7%, respectively. In patients with stage IV CDCK treated with surgery alone, chemotherapy alone, and surgery plus chemotherapy, the median survival time was 5 months, 9 months, and 14 months, respectively (P =0.024). Multivariate Cox regression analysis showed surgery, chemotherapy, stage, regional lymph node metastasis, and distant metastasis were independent prognostic factors for patients with CDCK.

Conclusions

CDCK is an uncommon malignant renal carcinoma, and its incidence is decreasing based on the analysis of current data. CDCK is a high stage, regional lymph-nodes positive, and metastatic disease. Compared with surgery alone or chemotherapy alone, patients with stage IV could gain survival benefit from surgery combined with chemotherapy.

Renal Crest Proliferative Lesions in Cats with Chronic Kidney Disease

In a histopathological study of the renal crest (RC) of kidneys of cats with chronic kidney disease (CKD), 58/90 (64%) had epithelial proliferation. Of these, 33 cats had hyperplasia of the collecting duct (CD) epithelium (CDH) alone, eight had hyperplasia of the urothelium covering the RC (RCUH), of which one had concurrent abaxial renal pelvic urothelial hyperplasia (UH), and eight had both CDH and RCUH. CDH or RCUH were present in five cats with marked dysplasia of the CD epithelium (CDD) and four cats with invasive carcinomas, which also had epithelial dysplasia. All nine cats with marked dysplasia or neoplasia of the RC also had substantially altered RC contours due to focal haemorrhage, papillary necrosis or fibrosis. Three of the carcinomas had a strong desmoplastic response. In control cats, both urothelial (RC and renal pelvis) and tubular (CD and distal tubular) cells were immunopositive for cytokeratin (CK; AE1/AE3), tubular epithelial cells were positive for vimentin (Vim) and aquaporin 2 (Aq2), while urothelial cells were positive for p63. PAX8 immunolabelling was difficult to validate. CD and UH labelling was similar to control tissue. While urothelial dysplasia had the same immunolabelling pattern as UH and control tissue, CDD was generally immunonegative for Aq2. As immunolabelling of the four carcinomas did not distinguish between tubular and urothelial origin, with three positive for both Vim and p63, all were broadly designated as RC carcinomas. Overall, proliferative epithelial lesions are common in cats with CKD and form a continuum from simple hyperplasia to neoplasia of the urothelium or CD of the RC.

Cysteamine-bicalutamide combination therapy corrects proximal tubule phenotype in cystinosis

Nephropathic cystinosis is a severe monogenic kidney disorder caused by mutations in CTNS, encoding the lysosomal transporter cystinosin, resulting in lysosomal cystine accumulation. The sole treatment, cysteamine, slows down the disease progression, but does not correct the established renal proximal tubulopathy. Here, we developed a new therapeutic strategy by applying omics to expand our knowledge on the complexity of the disease and prioritize drug targets in cystinosis. We identified alpha-ketoglutarate as a potential metabolite to bridge cystinosin loss to autophagy, apoptosis and kidney proximal tubule impairment in cystinosis. This insight combined with a drug screen revealed a bicalutamide-cysteamine combination treatment as a novel dual-target pharmacological approach for the phenotypical correction of cystinotic kidney proximal tubule cells, patient-derived kidney tubuloids and cystinotic zebrafish.

Culture and analysis of kidney tubuloids and perfused tubuloid cells-on-a-chip

Advanced in vitro kidney models are of great importance to the study of renal physiology and disease. Kidney tubuloids can be established from primary cells derived from adult kidney tissue or urine. Tubuloids are three-dimensional multicellular structures that recapitulate tubular function and have been used to study infectious, malignant, metabolic, and genetic diseases. For tubuloids to more closely represent the in vivo kidney, they can be integrated into an organ-on-a-chip system that has a more physiological tubular architecture and allows flow and interaction with vasculature or epithelial and mesenchymal cells from other organs. Here, we describe a detailed protocol for establishing tubuloid cultures from tissue and urine (1-3 weeks), as well as for generating and characterizing tubuloid cell-derived three-dimensional tubular structures in a perfused microfluidic multi-chip platform (7 d). The combination of the two systems yields a powerful in vitro tool that better recapitulates the complexity of the kidney tubule with donor-specific properties.

The Differential Diagnosis of Medullary-Based Renal Masses

CONTEXT.—

Renal malignancies can be divided into cortical- and medullary-based tumors, the latter of which classically infiltrate the renal parenchyma by extending between nonneoplastic structures. Although high-grade cortical tumors can rarely exhibit the same growth pattern, the infiltrative morphology should elicit a differential diagnosis to be considered in each case. However, these diagnoses can be challenging to distinguish, especially on small renal biopsy samples.

OBJECTIVE.—

To provide an overview of the clinical, gross, and microscopic findings; genetic and molecular alterations; and immunohistochemical evaluation of medullary-based renal tumors and other tumor types with overlapping morphologies and growth patterns.

DATA SOURCES.—

Literature review and personal observations were used to compile the information in this review.

CONCLUSIONS.—

Collecting duct carcinoma is a prototypical medullary-based tumor, and although diagnostic criteria exist, it remains a diagnosis of exclusion, especially with ancillary techniques aiding the recognition of established as well as more recently described neoplasms. Other medullary-based malignancies included in the differential diagnosis include renal medullary carcinoma/renal cell carcinoma unclassified with medullary phenotype, fumarate hydratase-deficient renal cell carcinoma, and upper tract urothelial carcinoma. Moreover, other rare entities should be excluded, including metastatic carcinoma, lymphoma, and melanoma. In addition to potential prognostic differences, accurate diagnoses can have important surgical and clinical management implications.

Bellini duct carcinoma

The modern era has brought an appreciation that renal cell carcinoma (RCC) includes diverse subtypes derived from the various parts of the nephron, each with its distinctive genetic basis and tumor biology. Carcinoma of the collecting ducts of Bellini (CDC) is a rare subtype of RCC, with a predictably poor prognosis. This rare subtype represents less than 1% of all kidney carcinomas. It derives from presumably numerous chromosomal losses. It is of chief importance to differentiate CDC from other types of renal cell cancer. Typically, it is characterized by a firm, centrally located tumor with infiltrative borders. Regarding the histopathologic characteristics, we can find complex, highly infiltrative cords with inflamed (desmoplastic) stroma, with high-grade nuclei and mitoses. Most reported cases of CDC had been high grade, advanced stage, and unresponsive to conventional therapies. This rare form of disease highlights the importance of multidisciplinary teams in the management of cancer patients.

Hereditary leiomyomatosis and renal cell carcinoma syndrome-associated renal cell carcinoma: Morphological appraisal with a comprehensive review of differential diagnoses

Hereditary leiomyomatosis and renal cell carcinoma (HLRCC) is an autosomal dominant syndrome wherein affected individuals are at risk for the development of cutaneous leiomyomas, early-onset multiple uterine leiomyomas, and an aggressive subtype of renal cell cancer. HLRCC is caused by germline mutations in the fumarate hydratase (FH) gene, which inactivates the enzyme and alters the function of the tricarboxylic acid/Krebs cycle. This article reviews the hitherto described morphologic features of HLRCC-associated renal cell carcinoma (RCC) and outlines the differential diagnosis and ancillary use of immunohistochemistry and molecular diagnostics for these tumors. The morphologic spectrum of HLRCC-associated RCC is wide and histologic features, including tumor cells with prominent nucleoli, perinucleolar halos, and multiple architectural patterns within the same tumor, which are suggestive of this diagnosis. FH immunohistochemistry in conjunction with genetic counseling and germline FH testing are the important parameters for detection of this entity. These kidney tumors warrant prompt treatment as even smaller sized lesions can demonstrate aggressive behavior and systemic oncologic treatment in metastatic disease should, if possible, be part of a clinical trial. Screening procedures in HLRCC families should preferably be evaluated in large cohorts.

Renal Cell Tumors: Molecular Findings Reshaping Clinico-pathological Practice

Over the past 20 years, the number of subtypes of renal epithelial cell neoplasia has grown. This growth has resulted from detailed histological and immunohistochemical characterization of these tumors and their correlation with clinical outcomes. Distinctive molecular phenotypes have validated the unique nature of many of these tumors. This growth of unique renal neoplasms has continued after the 2016 World Health Organization (WHO) Classification of Tumours. A consequence is that both the pathologists who diagnose the tumors and the clinicians who care for these patients are confronted with a bewildering array of renal cell carcinoma variants. Many of these variants have important clinical features, i.e. familial or syndromic associations, genomics alterations that can be targeted with systemic therapy, and benignancy of tumors previously classified as carcinomas. Our goal in the review is to provide a practical guide to help recognize these variants, based on small and distinct sets of histological features and limited numbers of immunohistochemical stains, supplemented, as necessary, with molecular features.

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.

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.

Clinical Features and Prognostic Outcome of Renal Collecting Duct Carcinoma: 12 Cases from a Single Institution

Purpose

Collecting duct carcinoma (CDC) is extremely rare and has high malignancy and poor prognosis. The purpose of this research is to explore the clinical characteristic, imaging, pathological diagnosis, treatment and prognostic outcome of CDCs.

Materials and Methods

The clinical data of 12 CDC cases who had been surgically treated between August 2007 and August 2017 and verified the diagnosis of CDC by postoperative pathological and/or immunohistochemical staining (IHC) results were retrospectively analyzed, and related works of literature were reviewed. And Kaplan-Meier survival analysis was used to draw the survival curve and to calculate the survival rate and the median survival time.

Results

According to the TNM stage system, 4 cases were in stage I, 2 in stage II,3 in stage III, and 3 in stage IV. On the computed tomograph and magnetic resonance imaging, CDC displayed that various shapes, unclear boundary and invasive growth into the renal parenchyma. Compared with small CDCs which did not change the contour of the kidney, large CDCs presented various imaging features. Microscopically, the typical morphology of CDCs was that collecting ducts or tubules were obviously infiltrated by tumor cells. A tubular, papillary, tubulopapillary or solid architectures with desmoplasia were often presented. And tumor cells had high-grade cytology or an infiltrative growth pattern. Necrosis of tumor cells also was common in many cases. The expression of biomarkers, such as PAX-8, INI-1, 34βE12, CK19, PAX-2, and vimentin, in most patients was detected by IHC. Eleven of all 12 cases received radical surgery, of whom 5 patients died 3–11 months after surgery, and 1 case having undergone interventional embolization therapy died at 6 months after treatment due to multiple metastases. And 1 lost to contact. The overall 1-, 2-, and 5-year survival rates were 45.5%, 36.4%, and 8.8%, respectively, and the median survival time (MST) was 11 months.

Conclusion

CDC has an aggressive clinical course, with a poor prognosis. The best way to treat CDC suspected by imaging examinations is radical surgery which can contribute to confirm the correct histopathological type. And post-operation follow-up is necessary.

An Algorithmic Immunohistochemical Approach to Define Tumor Type and Assign Site of Origin

Immunohistochemistry represents an indispensable complement to an epidemiology and morphology-driven approach to tumor diagnosis and site of origin assignment. This review reflects the state of my current practice, based on 15-years' experience in Pathology and a deep-dive into the literature, always striving to be better equipped to answer the age old questions, "What is it, and where is it from?" The tables and figures in this manuscript are the ones I "pull up on the computer" when I am teaching at the microscope and turn to myself when I am (frequently) stuck. This field is so exciting because I firmly believe that, through the application of next-generation immunohistochemistry, we can provide better answers than ever before. Specific topics covered in this review include (1) broad tumor classification and associated screening markers; (2) the role of cancer epidemiology in determining pretest probability; (3) broad-spectrum epithelial markers; (4) noncanonical expression of broad tumor class screening markers; (5) a morphologic pattern-based approach to poorly to undifferentiated malignant neoplasms; (6) a morphologic and immunohistochemical approach to define 4 main carcinoma types; (7) CK7/CK20 coordinate expression; (8) added value of semiquantitative immunohistochemical stain assessment; algorithmic immunohistochemical approaches to (9) "garden variety" adenocarcinomas presenting in the liver, (10) large polygonal cell adenocarcinomas, (11) the distinction of primary surface ovarian epithelial tumors with mucinous features from metastasis, (12) tumors presenting at alternative anatomic sites, (13) squamous cell carcinoma versus urothelial carcinoma, and neuroendocrine neoplasms, including (14) the distinction of pheochromocytoma/paraganglioma from well-differentiated neuroendocrine tumor, site of origin assignment in (15) well-differentiated neuroendocrine tumor and (16) poorly differentiated neuroendocrine carcinoma, and (17) the distinction of well-differentiated neuroendocrine tumor G3 from poorly differentiated neuroendocrine carcinoma; it concludes with (18) a discussion of diagnostic considerations in the broad-spectrum keratin/CD45/S-100-"triple-negative" neoplasm.

[Characterization of different renal cell carcinoma entities]

BACKGROUND

In recent years, the characterization of different renal cell carcinoma entities has significantly improved, in particular due to molecular typing.

OBJECTIVES

Classical, accepted and emerging renal cell carcinoma entities are described.

MATERIALS AND METHODS

A literature search was performed, followed by evaluation and description of the literature focusing on different renal cell carcinoma entities.

RESULTS

Classical renal cell carcinoma entities such as clear cell carcinoma, papillary renal cell carcinoma and chromophobe renal cell carcinoma have been expanded in particular by molecular techniques to include, for example, translocation carcinoma or carcinoma with mutations in genes of the mitochondrial energy metabolism. Some rare entities have been accepted by the World Health Organization (WHO) classification, while some are considered as emerging entities.

CONCLUSIONS

A range of newly accepted and emerging renal cell carcinoma entities have been introduced in the 2016 WHO classification. A precise and correct diagnosis is of major importance regarding the prognostic assessment, potential new therapeutic strategies and possible hereditary associations.

Bellini Duct Carcinoma Misdiagnosed with Urothelial Papillary Carcinoma

Background

Collecting (Bellini) duct carcinoma (CDC) or Bellini duct carcinoma (BDC) is a rare subtype of kidney tumors, accounting for less than 3% and known to have the worst prognosis. It is known to have multiple clinical presentations; this is why it can be easily misdiagnosed. The aim of this article is to present a case of CDC that was initially misdiagnosed with urothelial papillary carcinoma (UPC) in a 41-year-old male. Case Presentation. Our patient presented with a left flank pain evolving for one month and one episode of gross macroscopic hematuria. Upon presentation, he had left costovertebral angle tenderness. Initial lab tests were normal. Computed tomography revealed a 5 cm solid mass of the left renal pelvis and multiple infracentimetric perihilar lymph nodes. Subsequently, the patient had left nephroureterectomy. Microscopic examination showed the presence of a high-grade urothelial papillary carcinoma of the renal pelvis' lumen. All four of the dissected lymph nodes showed disease metastasis. Three years after establishing the diagnosis, the patient presented again for chronic abdominal pain, with a recent history of weight loss. CT scan showed a left paraaortic mass infiltrating the left psoas muscle over a length of 12 cm. Immunohistochemical profiling of this mass confirmed the diagnosis of Bellini duct carcinoma, rejecting the initial diagnosis of UPC. Therefore, the patient required a cisplatin-gemcitabine-based chemotherapy regimen.

Conclusion

BDC remains one of the rare aggressive subtypes of RCC, having a multitude of initial clinical presentations and an unfavorable prognosis. In this patient, CDC was masquerading as a transitional cell carcinoma that should always be kept in mind as a possible presentation. Corresponding early imaging and histopathology exams are primordial for a correct diagnosis and thus a better prognosis.

Collecting ducts carcinoma: An orphan disease. Literature overview and future perspectives

Collecting ducts carcinoma (CDC) is a rare and aggressive histological subtype of renal cancer accounting for only 1% of renal tumors. Usually patients present in bad clinical conditions due to a symptomatic disease with synchronous metastasis. Due to the rarity of CDC, data from prospective trials evaluating the best treatment for these patients are limited. The prognosis is poor with a median overall survival of around 11 months for patients with metastatic disease. The best treatment option today is considered a doublet chemotherapy with platinum salt plus gemcitabine as a result from a prospective phase II trial, but survival outcomes remain unsatisfactory. The interest in the in-depth understanding the biology of this orphan disease is growing, leading to find potential new biological-driven treatment approaches. Here we review the up-to-date literature evidences to address the best management of this rare and unfavorable clinical condition.

Practical Application of Lineage-Specific Immunohistochemistry Markers: Transcription Factors (Sometimes) Behaving Badly

CONTEXT.—

Transcription factors (TFs) are proteins that regulate gene expression and control RNA transcription from DNA. Lineage-specific TFs have increasingly been used by pathologists to determine tumor lineage, especially in the setting of metastatic tumors of unknown primary, among other uses. With experience gathered from its daily application and increasing pitfalls reported from immunohistochemical studies, these often-touted highly specific TFs are not as reliable as once thought.

OBJECTIVES.—

To summarize the established roles of many of the commonly used TFs in clinical practice and to discuss known and potential sources for error (eg, false-positivity from cross-reactivity, aberrant, and overlap "lineage-specific" expression) in their application and interpretation.

DATA SOURCES.—

Literature review and the authors' personal practice experience were used. Several examples selected from the University Health Network (Toronto, Ontario, Canada) are illustrated.

CONCLUSIONS.—

The application of TF diagnostic immunohistochemistry has enabled pathologists to better assess the lineage/origin of primary and metastatic tumors. However, the awareness of potential pitfalls is essential to avoid misdiagnosis.

Renal medullary carcinoma in a young mixed-race man in Japan

Renal medullary carcinoma (RMC) is a rare and aggressive cancer associated with the sickle cell trait. The diagnosis of RMC depends on recognition of its histologic features and immunohistochemical deficiency of INI1, but correct diagnosis is sometimes difficult, especially if a patient's information on race, past, and family medical history is unclear. At present, this is the first report on RMC in Japan.

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.

The detection of PAX8 in human upper urinary tract urothelial carcinoma

Upper urinary tract urothelial carcinomas (UUT-UCs) are defined as malignant neoplasms of the urothelium from the upper urinary tract, including renal calyces, the renal pelvis and the distal ureter. The natural attributes of UUT-UCs differ from those of bladder cancer. The aim of the present study was to investigate PAX8 expression in the normal urothelium and in urothelial carcinomas (UCs) of the upper urinary tract. Immunohistochemistry was conducted in 35 cases of renal pelvic and 30 cases of ureteral papillary UCs and the adjacent normal urothelium respectively. PAX8 mRNA expression was evaluated by RT-PCR in a different set of normal urothelial mucosa of the urinary tract and UUT-UCs. In immunohistochemical studies, the positive rates of PAX8 staining in UCs of the renal pelvis and ureter were 17% and 6.6% respectively, presenting focally positive in most cases, while the positive rates in the adjacent normal epithelia of the pelvis and ureter were 100% and 93% respectively. PAX8 mRNA was detected in all of the tumors and adjacent normal urothelial mucosa specimens of the upper urinary tract. 4 types of PAX8 isoforms, PAX8a, PAX8b, PAX8c and PAX8e, were detected in UUT-UCs in this study. As in bladder cancer, PAX8 expression was highly heterogeneous in terms of the splicing mRNA isoforms, with the different isoforms differentially expressed in the UUT-UCs. Among the 4 types of PAX8 isoforms, the PAX8e isoform was found in almost all UUT-UCs tumor tissues, but the PAX8d isoform was not detected in UUT-UCs that were different from the transcriptional splicing patterns of PAX8 in bladder cancer reported in the literature. In addition, the above 4 types of PAX8 splicing isoforms were simultaneously detected in almost all of the normal mucosal epithelia of the upper urinary tract, which was very different from that of bladder mucosa. Further studies are suggested to reveal whether or not the differences in natural attributes between UCs of the upper and lower urinary tracts are related to their PAX8 transcriptional splicing patterns.

High grade infiltrative adenocarcinomas of renal cell origin: New insights into classification, morphology, and molecular pathogenesis

Collecting duct carcinoma was described over 30 years ago as a renal tumor, based in the medullary collecting system, with tubulopapillary morphology, prominent infiltrative growth, and stromal desmoplasia. While diagnostic workup has always emphasized exclusion of upper tract urothelial carcinoma and metastatic adenocarcinoma to the kidney, the molecular era of renal cell carcinoma classification has enabled recognition of and provided tools for diagnosis of new entities in this morphologic differential. In this review, we consider these developments, with emphasis on renal medullary carcinoma, closely related renal cell carcinoma, unclassified with medullary phenotype, and fumarate hydratase-deficient renal cell carcinoma. Integration of ancillary studies with suggestive patterns of morphology is emphasized for practical implementation in contemporary diagnosis, and several emerging tumor types in the morphologic differential are presented.

Morphological spectrum of renal cell carcinoma, unclassified: an analysis of 136 cases

AIMS

Renal cell carcinoma, unclassified (RCCU) is a category that includes a morphologically and biologically heterogeneous group of tumours that are unable to be diagnosed as other well-defined entities. We aim to describe the morphological findings of tumours within this category and to determine the most frequent morphological features leading to classification difficulty.

METHODS AND RESULTS

One hundred and thirty-six cases of RCCU were examined. Patients ranged in age from 23 to 87 years. Seventy-seven patients were men and 59 were women. International Society of Urological Pathology (ISUP) grade was most commonly 3 (n = 66), followed by 2 (n = 42) and 4 (n = 28). Tumour size ranged from 0.6 to 24.9 cm. The American Joint Committee on Cancer (AJCC) pathological T categories included pT1a (n = 50), pT1b (n = 14), pT2a (n = 7), pT2b (n = 4), pT3a (n = 50) and pT4 (n = 9). Forty-four cases included lymph node(s), 41% of which (n = 18) had metastases. Tumours were assessed for a variety of histological features and assigned to the following morphological groups: predominantly oncocytoma/chromophobe RCC-like; clear cell RCC-like; papillary RCC-like; collecting duct-like; and pure sarcomatoid differentiation. The majority of the oncocytoma/chromophobe and clear cell RCC-like phenotypes were low stage (pT1 or pT2). The papillary RCC-like, collecting duct-like and pure sarcomatoid phenotypes were mainly high stage (pT3 or pT4).

CONCLUSIONS

Renal cell carcinoma, unclassified is a term that encompasses tumours with a variety of morphological features and a wide biological spectrum. The most common source of diagnostic difficulty was tumours composed of predominantly eosinophilic cells.

Paraneoplastic Glomerulopathy in a Case of Collecting Duct Renal Cell Carcinoma

Paraneoplastic glomerulopathy has been described in established cases of the solid tumors of lung, gastrointestinal system, breast, etc., and rarely in patients with Renal Cell Carcinoma (RCC). Studies on secondary glomerular diseases have described a higher incidence of IgA nephropathy in patients with RCC compared to membranous glomerulopathy, which are commonly reported in malignancies of the lung and gastrointestinal tract. Collecting Duct Carcinoma (CDC), a rare high grade adenocarcinoma accounts for <1% of all renal malignancies. It arises from the cells of the collecting ducts of Bellini. We report a case of an elderly male who was diagnosed to have a disseminated CDC during his evaluation for nephrotic syndrome. Renal biopsy was suggestive of a secondary membranous glomerulonephropathy.

Clinicopathologic and Molecular Pathology of Collecting Duct Carcinoma and Related Renal Cell Carcinomas

Collecting duct carcinoma (CDC) and related tumors [ie, renal medullary carcinoma (RMC)] are rare types of highly aggressive renal cell carcinomas (RCC) with poor prognosis. Because of the rarity and diagnostic uncertainty of them, their molecular pathology and significance have not yet been fully elucidated. CDC, RMC, fumarate hydratase-deficient RCC (including hereditary leiomyomatosis and RCC-associated RCC HLRCC-RCC), and recently reported anaplastic lymphoma kinase (ALK)-rearrangement RCC have significant morphologic overlaps, but they are separately distinct entities having different molecular pathway and clinical settings. CDC is more likely to occur in middle to old age population with immunoreactivity for PAX8 and integrase interactor-1 proteins (INI-1). Various chromosomal and genomic alterations have been reported with inconsistent results. In contrast, RMC is more likely to occur in younger patients with sickle cell trait. In RMC, loss of INI-1 expression and OCT3/4 expression are distinguished compared with other RCCs. Finally, ALK-rearrangement RCC seems to have 2 different clinical settings, one with sickle cell trait (VCL-ALK fusion) and the other without (other fusions such as TPM3-ALK, EML4-ALK, and STRN-ALK fusions). Interestingly, VCL-ALK fusion was found in pediatric patients with sickle cell trait, whereas other fusions were detected in adolescent or adult without sickle cell trait. Taken together, CDC and related tumors such as RMC, fumarate hydratase-deficient RCC (including hereditary leiomyomatosis and RCC-associated RCC), and ALK-rearrangement RCC are the distinct entities and their recognition is important for the development of future personalized therapeutic options. This review updates the clinicopathologic features of these tumors with overlapping morphology and outcome.

Correlating Preoperative Imaging with Histologic Subtypes of Renal Cell Carcinoma and Common Mimickers

Renal cell carcinoma (RCC) consists of distinct subtypes that have unique pathologic and imaging features as well as specific cytogenetic and molecular characteristics. As the prognosis and therapeutic strategies may differ for each subtype, correlation of the preoperative imaging with the pathologic findings is of great clinical relevance. In addition, differentiation of RCC from benign entities is ideal in order to prevent overtreatment. However, a noninvasive diagnosis with imaging alone is not always straightforward due to the overlapping appearance of RCC with benign lesions such as fat-poor angiomyolipoma and oncocytoma. With new imaging modalities, there have been significant improvements in correlating preoperative imaging with pathologic characteristics. These new discoveries are able to aid in a more specific, noninvasive, diagnosis that in turn helps direct patient management.

Adult Renal Cell Carcinoma: A Review of Established Entities from Morphology to Molecular Genetics

According to the current World Health Organization (WHO), renal cell carcinomas (RCCs) that primarily affect adults are classified into 8 major subtypes. Additional emerging entities in renal neoplasia have also been recently recognized and these are discussed in further detail by Mehra et al (Emerging Entities in Renal Neoplasia, Surgical Pathology Clinics, 2015, Volume 8, Issue 4). In most cases, the diagnosis of a RCC subtype can be based on morphologic criteria, but in some circumstances the use of ancillary studies can aid in the diagnosis. This review discusses the morphologic, genetic, and molecular findings in RCCs previously recognized by the WHO, and provides clues to distinction from each other and some of the newer subtypes of RCC. As prognosis and therapeutic options vary for the different subtypes of RCC, accurate pathologic distinction is critical for patient care.

Unique Transcriptomic Profile of Collecting Duct Carcinomas Relative to Upper Tract Urothelial Carcinomas and other Kidney Carcinomas

Collecting duct carcinoma (CDC) is a kidney cancer subtype that is thought to arise from principal cells in distal parts of the collecting ducts. Some studies suggested an overlap of CDC with upper tract urothelial carcinoma (UTUC), making the pathological diagnosis challenging. Herein, we performed for the first time transcriptome sequencing of CDC and compared them to UTUC and renal cell carcinoma subtypes. We discovered that CDC displays a unique transcriptomic signature among kidney cancer subtypes, with a putative cell of origin in the distal convoluted tubules. Hierarchical unsupervised clustering reveals that the CDC signature is closer to that of other RCC subtypes than to UTUC, which is similar to that of bladder carcinoma. CDC is characterized by a metabolic shift, with impairment of oxidoreductase activity, pyruvate metabolism and the tricarboxlyic acid cycle, as well as an immunogenic response consistent with increased tumor infiltrating lymphocytes, particularly within metastatic cases. In addition, pathways differentially altered between CDC and UTUC point to a basal-like phenotype of CDC in contrast to the luminal-like signature of UTUC. We conclude that CDC harbors a pathognomonic transcriptomic signature characterized by immunogenic and a metabolic aberrations, indicating that targeting these processes might provide therapeutic options for patients.

PAX8 is transcribed aberrantly in cervical tumors and derived cell lines due to complex gene rearrangements

The transcription factor PAX8, a member of the paired box-containing gene family with an important role in embryogenesis of the kidney, thyroid gland and nervous system, has been described as a biomarker in tumors of the thyroid, parathyroid, kidney and thymus. The PAX8 gene gives rise to four isoforms, through alternative mRNA splicing, but the splicing pattern in tumors is not yet established. Cervical cancer has a positive expression of PAX8; however, there is no available data determining which PAX8 isoform or isoforms are present in cervical cancer tissues as well as in cervical carcinoma-derived cell lines. Instead of a differential pattern of splicing isoforms, we found numerous previously unreported PAX8 aberrant transcripts ranging from 378 to 542 bases and present in both cervical carcinoma-derived cell lines and tumor samples. This is the first report of PAX8 aberrant transcript production in cervical cancer. Reported PAX8 isoforms possess differential transactivation properties; therefore, besides being a helpful marker for detection of cancer, PAX8 isoforms can plausibly exert differential regulation properties during carcinogenesis.

Papillary or pseudopapillary tumors of the kidney

Papillary architecture is one of the most common morphological patterns in renal cell neoplasms. Many renal cell neoplasms can also exhibit, diffusely or focally, papillary growth pattern. This article reviews all the renal cell neoplasms with papillary or pseudopapillary architecture, with an emphasis on recently described new histological types. New insights into the "old" entities, including their immunohistochemical and genetic features, will also be discussed.

Immunohistochemistry in undifferentiated neoplasm/tumor of uncertain origin

CONTEXT

Immunohistochemistry has become an indispensable ancillary study in the identification and classification of undifferentiated neoplasms/tumors of uncertain origin. The diagnostic accuracy has significantly improved because of the continuous discoveries of tissue-specific biomarkers and the development of effective immunohistochemical panels.

OBJECTIVES

To identify and classify undifferentiated neoplasms/tumors of uncertain origin by immunohistochemistry.

DATA SOURCES

Literature review and authors' research data and personal practice experience were used.

CONCLUSIONS

To better guide therapeutic decisions and predict prognostic outcomes, it is crucial to differentiate the specific lineage of an undifferentiated neoplasm. Application of appropriate immunohistochemical panels enables the accurate classification of most undifferentiated neoplasms. Knowing the utilities and pitfalls of each tissue-specific biomarker is essential for avoiding potential diagnostic errors because an absolutely tissue-specific biomarker is exceptionally rare. We review frequently used tissue-specific biomarkers, provide effective panels, and recommend diagnostic algorithms as a standard approach to undifferentiated neoplasms.

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.

PAX-8 expression in renal tumours and distant sites: a useful marker of primary and metastatic renal cell carcinoma?

AIMS

Immunohistochemical stains have greatly improved the diagnostic accuracy of renal cell carcinoma (RCC) for primary and distant tumours. We evaluate a marker that has recently been incorporated in clinical practice, PAX-8, in primary and metastatic RCCs.

METHODS

Two distinct tissue microarrays were used, one consisting of over 334 renal tumours, 294 with adjacent normal kidney and the other with 40 matched nephrectomy and metastatic sites of RCC. PAX-8 expression was assessed by a method of quantitative immunofluorescence.

RESULTS

PAX-8 was positive in 96% (146/152) of normal renal tissue and 83% (227/272) of renal tumours. PAX-8 staining was positive in clear cell, papillary and chromophobe tumours in 80% (165/207), 95% (39/41) and 100% (6/6) of samples, respectively. Overall, intensity of PAX-8 expression was significantly higher in RCC metastatic sites than in the primary site (p=0.0047), however, in matched sites there was no statistically significant difference in the proportion of positive versus negative specimens (p=0.274).

CONCLUSIONS

As the role of molecular markers expands in the diagnostic algorithm, this study confirms that PAX-8 expression is a useful diagnostic marker for RCC. PAX-8 expression was found in the primary tumour and distant sites. Compared with normal tissue and other histological types, clear cell RCC has lower PAX-8 expression and is less frequently positive, therefore, the lack of expression does not exclude a tumour of renal origin.

Upper urinary tract urothelial carcinoma with intratubular spread

Upper urinary tract urothelial cell carcinomas (UUT-UCs) are uncommon and are defined as urothelial carcinoma involving the urinary tract from the renal calyces, renal pelvis to the distal ureter. One well-known an peculiar histopathological finding in UUT-UC is urothelial carcinoma with intratubular spread (retrograde spread within renal tubules). However, this special feature has not been systematically studied. We therefore collected a total of 53 consecutive cases of upper urinary tract urothelial carcinomas (UUT-UCs), and studied the clinical and pathological features of intratubular spread (IS). A cocktail stain comprised of antibodies PAX8 and p63 together with PAS was validated and employed to facilitate the study of intratubular spread. Seventeen cases (31.5%) showed intratubular spread demonstrated by either H&E stain and/or the cocktail stain. All of the 17 cases wit intratubular spread had tumor involvement of the renal calyx; the majority of these (14/17, 82.4%) were high grade urothelial carcinoma and the remainder (3/17, 17.6%) were low grade. 4 of 17cases (23.5%) were non-invasive. We classified intratubular spread into 4 different types, based on histopathological patterns: pagetoid, typical, florid, and secondary invasion from intratubular spread. In conclusion, study shows intratubular spread of urothelial carcinoma is fairly common phenomenon in UUT-UC and is associated with a variety of clinical-pathological features. High grade UUT-UC tends to have more extensive intratubular spread and secondary invasion into renal parenchyma. Distinct morphological characteristics as well as the staining pattern from a unique cocktail stain help to identify and evaluate intratubular spread of urothelial carcinoma. Recognizing these different types of intratubular spreading (IS) is crucial for accurate staging of some upper urinary tract urothelial carcinomas (UUT-UCs).

Recent advances of immunohistochemistry for diagnosis of renal tumors

The recent classification of renal tumors has been proposed according to genetic characteristics as well as morphological difference. In this review, we summarize the immunohistochemical characteristics of each entity of renal tumors. Regarding translocation renal cell carcinoma (RCC), TFE3, TFEB and ALK protein expression is crucial in establishing the diagnosis of Xp11.2 RCC, renal carcinoma with t(6;11)(p21;q12), and renal carcinoma with ALK rearrangement, respectively. In dialysis-related RCC, neoplastic cells of acquired cystic disease-associated RCC are positive for alpha-methylacyl-CoA racemase (AMACR), but negative for cytokeratin (CK) 7, whereas clear cell papillary RCC shows the inverse pattern. The diffuse positivity for carbonic anhydrase 9 (CA9) is diagnostic for clear cell RCC. Co-expression of CK7 and CA9 is characteristic of multilocular cystic RCC. CK7 and AMACR are excellent markers for papillary RCC and mucinous tubular and spindle cell carcinoma. CD82 and epithelial-related antigen (MOC31) may be helpful in the distinction between chromophobe RCC and renal oncocytoma. WT1 and CD57 highlights the diagnosis of metanephric adenoma. The combined panel of PAX2 and PAX8 may be useful in the diagnosis of metastatic RCC.