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Introduction: IgG4-related disease (IgG4-RD) is a systemic immune-mediated disease that can involve nearly any organ. IgG4-RD can affect the kidney in different disease patterns, collectively referred to as IgG4-related kidney disease (IgG4-RKD)., Methods: We conducted a tissue-based cohort study with clinicopathological correlation in 125 patients with IgG4-RKD., Results: The mean age at biopsy ( n  = 120) or nephrectomy ( n  = 5) was 63 years; 80% were male. One hundred eighteen patients (94%) had IgG4-related tubulointerstitial nephritis (IgG4-TIN); 20 patients (16%) had IgG4-related membranous glomerulonephritis (IgG4-MGN; 13 with concurrent IgG4-TIN). The primary clinical indication for biopsy/nephrectomy was acute or chronic renal failure in 78%, proteinuria in 17%, and mass lesion(s) in 15% (with overlap in primary indication). Fifty-two percent patients (41/79) had abnormal radiographic findings, including masses in 30% (24/79). All patients with IgG4-MGN had proteinuria. Extrarenal involvement by IgG4-RD was present in 79%. Median serum creatinine at presentation was 2.5 mg/dl (range 0.7-12). Serum IgG and/or IgG4 was increased in 91% (53/58); hypocomplementemia was present in 56% (43/77). Light microscopy showed plasma cell-rich interstitial nephritis in all cases of IgG4-TIN. Ninety-two percent of patients showed increased IgG4+ plasma cells. Seven percent showed an acute interstitial nephritis (AIN) pattern, and 5% showed non-necrotizing arteritis. Tubular basement membrane immune deposits were present in 83% of IgG4-TIN. Treatment information was available for 71 patients; 62 were treated with immunosuppression. Of those with elevated creatinine, 72% (41/57) showed a treatment response., Conclusion: This largest tissue-based series more clearly defines the disease phenotype of IgG4-RKD., (© 2024 International Society of Nephrology. Published by Elsevier Inc.)

Atypical antiglomerular basement membrane (anti-GBM) nephritis can be defined as linear GBM staining for monotypic or polytypic immunoglobulin (Ig) by immunofluorescence (IF) without a diffuse crescentic pattern. We describe the clinicopathologic features of 6 patients (18 biopsies) in this first series of recurrent atypical anti-GBM nephritis after kidney transplantation. Recurrent glomerulonephritis occurred at a mean of 3.8 months posttransplant (range 1-7 months). Three index biopsies were for clinical indication, and 3 were protocol biopsies. Glomerular histologic changes were mild, with 2 showing segmental endocapillary hypercellularity, 1 focal glomerular microangiopathy, and the others no significant glomerular histologic changes. All 6 allografts showed monotypic linear glomerular Ig staining by IF: IgG kappa (n = 2), IgG lambda, IgA kappa, IgA lambda, and IgM lambda. Follow-up biopsies were available for 5 patients and showed similar histologic and IF findings without evidence of significant progression. No patients had detectable serum anti-GBM antibody or monoclonal proteins. The mean serum creatinine level on follow-up (24-62 months posttransplant) was 1.8 (range 0.93-2.77) mg/dL; no grafts were lost to recurrent disease. This series demonstrates that monotypic atypical anti-GBM recurs in the allograft and supports the idea that this disease is due to a circulating monoclonal protein., (Copyright © 2023 American Society of Transplantation & American Society of Transplant Surgeons. Published by Elsevier Inc. All rights reserved.)

Membranous nephropathy (MN) is a pattern of injury caused by autoantibodies binding to specific target antigens, with accumulation of immune complexes along the subepithelial region of glomerular basement membranes. The past 20 years have brought revolutionary advances in the understanding of MN, particularly via the discovery of novel target antigens and their respective autoantibodies. These discoveries have challenged the traditional classification of MN into primary and secondary forms. At least 14 target antigens have been identified, accounting for 80%-90% of cases of MN. Many of the forms of MN associated with these novel MN target antigens have distinctive clinical and pathologic phenotypes. The Mayo Clinic consensus report on MN proposes a 2-step classification of MN. The first step, when possible, is identification of the target antigen, based on a multistep algorithm and using a combination of serology, staining of the kidney biopsy tissue by immunofluorescence or immunohistochemistry, and/or mass spectrometry methodology. The second step is the search for a potential underlying disease or associated condition, which is particularly relevant when knowledge of the target antigen is available to direct it. The meeting acknowledges that the resources and equipment required to perform the proposed testing may not be generally available. However, the meeting consensus was that the time has come to adopt an antigen-based classification of MN because this approach will allow for accurate and specific MN diagnosis, with significant implications for patient management and targeted treatment., (Copyright © 2023 International Society of Nephrology and Mayo Foundation for Medical Education and Research. Published by Elsevier Inc. All rights reserved.)

Introduction: Kidney disease is a well-known extraintestinal manifestation (EIM) associated with inflammatory bowel disease (IBD), with a variety of underlying etiologies. However, little is known about the overall outcomes and predictors., Methods: This is a retrospective, observational cohort study. Patients with IBD in whom a native kidney biopsy was performed at Mayo Clinic (Rochester, MN) between 1994 and 2022, were included. Demographic, clinical, and histologic characteristics of prognostic interest were collected. The main outcomes were kidney failure, disease remission, kidney function changes at last follow-up, and death., Results: From a total cohort of 318 patients, we selected a study group of 111 patients followed-up with at our institution (45 ulcerative colitis [UC] and 66 Crohn's disease [CD]), with a mean age of 48 ± 17 years (40% females). IgA nephropathy (IgAN), chronic interstitial nephritis (CIN), and acute interstitial nephritis (AIN) were the most common diagnoses (22%, 19%, 13%, respectively). Median estimated glomerular filtration rate (eGFR) at presentation was 30 ml/min per 1.73 m 2 (interquartile range [IQR]: 17-54) and urinary protein-to-creatinine ratio [UPCR] 0.8 g/g (0.3-3.4), without differences between IBD types. During a median follow-up of 59 months (12-109), 29 patients (26%) reached kidney failure. By multivariable analysis, the main predictors of kidney failure were age (hazard ratio [HR]: 1.04; P  = 0.002), baseline eGFR (HR: 0.94; P  = 0.003) and histologic chronicity score (HR: 4.01; P  < 0.001). Therapeutic management varied according to underlying etiology. Global survival (kidney failure + death) was significantly better in patients who achieved complete or partial remission, or stabilization or improvement of kidney function., Conclusion: One-fourth of patients with IBD with kidney disease may reach kidney failure, and the main determinants of this outcome is age, baseline eGFR, and degree of chronicity in kidney biopsy., (© 2023 International Society of Nephrology. Published by Elsevier Inc.)

Membranous nephropathy (MN) is a pattern of injury caused by autoantibodies binding to specific target antigens, with accumulation of immune complexes along the subepithelial region of glomerular basement membranes. The past 20 years have brought revolutionary advances in the understanding of MN, particularly via the discovery of novel target antigens and their respective autoantibodies. These discoveries have challenged the traditional classification of MN into primary and secondary forms. At least 14 target antigens have been identified, accounting for 80%-90% of cases of MN. Many of the forms of MN associated with these novel MN target antigens have distinctive clinical and pathologic phenotypes. The Mayo Clinic consensus report on MN proposes a 2-step classification of MN. The first step, when possible, is identification of the target antigen, based on a multistep algorithm and using a combination of serology, staining of the kidney biopsy tissue by immunofluorescence or immunohistochemistry, and/or mass spectrometry methodology. The second step is the search for a potential underlying disease or associated condition, which is particularly relevant when knowledge of the target antigen is available to direct it. The meeting acknowledges that the resources and equipment required to perform the proposed testing may not be generally available. However, the meeting consensus was that the time has come to adopt an antigen-based classification of MN because this approach will allow for accurate and specific MN diagnosis, with significant implications for patient management and targeted treatment., (Copyright © 2023 International Society of Nephrology and Mayo Foundation for Medical Education and Research. Published by Elsevier Inc. All rights reserved.)

Objectives: There is a paucity of data on penile amyloidosis. We aimed to assess the frequency of different amyloid types in surgical specimens from the penis involved by amyloidosis and correlate relevant clinicopathologic parameters with proteomic findings., Methods: Since 2008, our reference laboratory has performed liquid chromatography/tandem mass spectrometry (LC-MS/MS) for amyloid typing. The institutional pathology archive and reference laboratory database were queried to retrospectively identify all penile surgical pathology specimens with LC-MS/MS results between January 1, 2008, and November 23, 2022. Archived H&E-stained and Congo red-stained sections were re-reviewed., Results: Twelve cases of penile amyloidosis were identified, which represented 0.35% (n = 3,456) of penile surgical specimens. AL-type amyloid was most frequent (n = 7), followed by keratin-type amyloid (n = 3) and ATTR (transthyretin)-type amyloid (n = 2). AL-type amyloid cases often showed diffuse dermal/lamina propria deposition, whereas all keratin-type amyloid cases were localized to the superficial dermis. Two cases with keratin-type amyloid had concomitant cutaneous findings (penile intraepithelial neoplasia and condyloma)., Conclusions: This series, the largest to date, demonstrates that penile amyloidosis has a heterogeneous proteomic landscape. To the best of our knowledge, this is the first study describing ATTR (transthyretin)-type penile amyloid., (© The Author(s) 2023. Published by Oxford University Press on behalf of American Society for Clinical Pathology. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

Background and Objectives: Urinary stone disease has been associated with inflammation, but the specific cell interactions that mediate events remain poorly defined. This study compared calcification and inflammatory cell patterns in kidney tissue from radical nephrectomy specimens of patients without and with a history of urinary stone disease., Design, Setting, Participants, & Measurements: Nontumor parenchyma of biobanked radical nephrectomy specimens from age- and sex-matched stone formers ( n =44) and nonstone formers ( n =82) were compared. Calcification was detected by Yasue staining and inflammatory cell populations by immunohistochemistry for CD68 (proinflammatory M1 macrophages), CD163 and CD206 (anti-inflammatory M2 macrophages), CD3 (T lymphocytes), and tryptase (mast cells). Calcifications and inflammatory cells were quantified in cortex and medulla using Image-Pro analysis software., Results: Calcification in the medulla of stone formers was higher than in nonstone formers ( P <0.001). M1 macrophages in the cortex and medulla of stone formers were greater than in nonstone formers ( P <0.001), and greater in stone former medulla than stone former cortex ( P =0.02). There were no differences in age, sex, body mass index, tumor characteristics (size, stage, or thrombus), vascular disease status, or eGFR between the groups. M2 macrophages, T lymphocytes, and mast cells did not differ by stone former status. There was a correlation between M1 macrophages and calcification in the medulla of stone formers (rho=0.48; P =0.001) and between M2 macrophages and calcification in the medulla of nonstone formers (rho=0.35; P =0.001). T lymphocytes were correlated with calcification in the cortex of both nonstone formers (rho=0.27; P =0.01) and stone formers (rho=0.42; P =0.004), whereas mast cells and calcification were correlated only in the cortex of stone formers (rho=0.35; P =0.02)., Conclusions: Higher medullary calcification stimulated accumulation of proinflammatory rather than anti-inflammatory macrophages in stone formers., (Copyright © 2022 by the American Society of Nephrology.)

Histologic findings on 1-year biopsies such as inflammation with fibrosis and transplant glomerulopathy predict renal allograft loss by 5 years. However, almost half of the patients with graft loss have a 1-year biopsy that is either normal or has only interstitial fibrosis. The goal of this study was to determine if there was a gene expression profile in these relatively normal 1-year biopsies that predicted subsequent decline in renal function. Using transcriptome microarrays we measured intragraft mRNA levels in a retrospective Discovery cohort (170 patients with a normal/minimal fibrosis 1-year biopsy, 54 with progressive decline in function/graft loss and 116 with stable function) and developed a nested 10-fold cross-validated gene classifier that predicted progressive decline in renal function (positive predictive value = 38 ± 34%%; negative predictive value = 73 ± 30%, c-statistic = .59). In a prospective, multicenter Validation cohort (270 patients with Normal/Interstitial Fibrosis [IF]), the classifier had a 20% positive predictive value, 85% negative predictive value and .58 c-statistic. Importantly, the majority of patients with graft loss in the prospective study had 1-year biopsies scored as Normal or IF. We conclude predicting graft loss in many renal allograft recipients (i.e., those with a relatively normal 1-year biopsy and eGFR > 40) remains difficult., (© 2021 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

Objective: To compare coronavirus disease 2019 (COVID-19) acute kidney injury (AKI) to sepsis-AKI (S-AKI). The morphology and transcriptomic and proteomic characteristics of autopsy kidneys were analyzed., Patients and Methods: Individuals 18 years of age and older who died from COVID-19 and had an autopsy performed at Mayo Clinic between April 2020 to October 2020 were included. Morphological evaluation of the kidneys of 17 individuals with COVID-19 was performed. In a subset of seven COVID-19 cases with postmortem interval of less than or equal to 20 hours, ultrastructural and molecular characteristics (targeted transcriptome and proteomics analyses of tubulointerstitium) were evaluated. Molecular characteristics were compared with archived cases of S-AKI and nonsepsis causes of AKI., Results: The spectrum of COVID-19 renal pathology included macrophage-dominant microvascular inflammation (glomerulitis and peritubular capillaritis), vascular dysfunction (peritubular capillary congestion and endothelial injury), and tubular injury with ultrastructural evidence of mitochondrial damage. Investigation of the spatial architecture using a novel imaging mass cytometry revealed enrichment of CD3 + CD4 + T cells in close proximity to antigen-presenting cells, and macrophage-enriched glomerular and interstitial infiltrates, suggesting an innate and adaptive immune tissue response. Coronavirus disease 2019 AKI and S-AKI, as compared to nonseptic AKI, had an enrichment of transcriptional pathways involved in inflammation (apoptosis, autophagy, major histocompatibility complex class I and II, and type 1 T helper cell differentiation). Proteomic pathway analysis showed that COVID-19 AKI and to a lesser extent S-AKI were enriched in necroptosis and sirtuin-signaling pathways, both involved in regulatory response to inflammation. Upregulation of the ceramide-signaling pathway and downregulation of oxidative phosphorylation in COVID-19 AKI were noted., Conclusion: This data highlights the similarities between S-AKI and COVID-19 AKI and suggests that mitochondrial dysfunction may play a pivotal role in COVID-19 AKI. This data may allow the development of novel diagnostic and therapeutic targets., (Copyright © 2021 The Authors. Published by Elsevier Inc. All rights reserved.)

Background: Patients with cryoglobulinemic vasculitis (CV) can develop disease flare after rituximab administration. The objective of our study was to describe the prevalence, clinical characteristics, predisposing factors, and outcomes of patients with rituximab-associated flare of CV., Methods: We conducted a retrospective study in a tertiary referral center until March 25, 2020., Results: Among 64 patients with CV who received rituximab therapy in our center, 14 (22%) developed disease flare. Median age was 67.5 years. Seven patients (50%) had type II CV and the other half had either type I ( n = 6) or type III ( n = 1). Twelve patients (86%) had an underlying B-cell lymphoproliferative disorder as the cause of their CV. CV flare occurred after a median time of 5.5 days (range: 2-8 days). The organ systems most involved were the skin ( n = 10), kidneys ( n = 5), and peripheral nerves ( n = 3). Five patients (36%) developed acute kidney injury (AKI), 3 of whom presented with nephritic syndrome secondary to biopsy-proven membranoproliferative glomerulonephritis. Treatment was directed against the underlying disease in addition to supportive care. Patients who developed flare were more likely to have B-cell lymphoproliferative disorder as the underlying etiology of their CV ( P  = 0.03). Eight patients (57%) died after a median time of 27 months., Conclusions: Rituximab-associated flare can occur in all types of CV, tends to arise approximately 2 days and less than 1 week after rituximab administration, and is more likely to happen in patients with an underlying B-cell lymphoproliferative disorder. It does not indicate treatment failure, and rituximab should not be abandoned altogether. AKI is a common manifestation, and mortality rate at 2 years is high., (© 2021 International Society of Nephrology. Published by Elsevier Inc.)

Low-grade oncocytic tumor of the kidney (LOT) is characterized by cytoplasmic eosinophilia and a CK7-positive/CD117-negative immunophenotype. Morphologically, they exhibit overlapping features with oncocytoma and chromophobe renal cell carcinoma. Our aim was to obtain long-term clinical follow-up data, clinicopathological and molecular characteristics, and incidence of LOT. Tissue microarrays were constructed from 574 tumors historically diagnosed as oncocytoma and surgically treated at Mayo Clinic between 1970 and 2012, and immunostained for CK7 and CD117. An extended immunophenotype was obtained on whole slide sections, along with FISH for CCND1 rearrangement status and chromosomal microarray for copy number status. In addition, two cases were retrospectively identified in a set of tuberous sclerosis complex (TSC)-associated neoplasms and three more cases diagnosed on needle core biopsies were obtained during routine clinical practice. Twenty-four cases of LOT were identified among 574 consecutive tumors diagnosed as oncocytoma and treated with partial or radical nephrectomy, corresponding to an incidence of 4.18% of tumors historically diagnosed as oncocytomas, and 0.35% of 6944 nephrectomies performed between 1970 and 2012. Overall, 29 cases of LOT were identified in three clinical settings: sporadic, TSC-associated, and end-stage renal disease (ESRD). Multifocality was seen only in the setting of TSC and ESRD. No metastases attributable to LOT were identified (median follow-up 9.6 years). There were no recurrent arm level copy number changes detected by chromosomal microarray and all tested cases were negative for CCND1 rearrangement by FISH. LOT is an uncommon eosinophilic renal neoplasm with an indolent prognosis that constitutes ∼4% of tumors historically diagnosed as oncocytoma. The morphologic, immunophenotypic, and molecular features of this neoplasm suggest it is a distinct entity of renal neoplasia., (Copyright © 2021 Elsevier Inc. All rights reserved.)

Backgrounds: Previous studies have demonstrated that excretion of urinary extracellular vesicles (EVs) from different nephron segments differs between kidney stone formers and non-stone formers (NSFs), and could reflect pathogenic mechanisms of urinary stone disease. In this study we quantified selected populations of specific urinary EVs carrying protein markers of immune cells and calcium/phosphorus physiology in calcium oxalate stone formers (CSFs) compared to non-stone formers (NSFs)., Methods: Biobanked urine samples from CSFs (n = 24) undergoing stone removal surgery and age- and sex- matched NSFs (n = 21) were studied. Urinary EVs carrying proteins related to renal calcium/phosphorus physiology (phosphorus transporters (PiT1 and PiT2), Klotho, and fibroblast growth factor 23 (FGF23); markers associated with EV generation (anoctamin-4 (ANO4) and Huntington interacting protein 1 (HIP1)), and markers shed from activated immune cells were quantified by standardized and published method of digital flow cytometry., Results: Urine excretion of calcium, oxalate, phosphorus, and calcium oxalate supersaturation (SS) were significantly higher in CSFs compared to NSFs (P < 0.05). Urinary excretion of EVs with markers of total leukocytes (CD45), neutrophils (CD15), macrophages (CD68), Klotho, FGF23, PiT1, PiT2, and ANO4 were each markedly lower in CSFs than NSFs (P < 0.05) whereas excretion of those with markers of monocytes (CD14), T-Lymphocytes (CD3), B-Lymphocytes (CD19), plasma cells (CD138 plus CD319 positive) were not different between the groups. Urinary excretion of EVs expressing PiT1 and PiT2 negatively (P < 0.05) correlated with urinary phosphorus excretion, whereas excretion of EVs expressing FGF23 negatively (P < 0.05) correlated with both urinary calcium and phosphorus excretion. Urinary EVs with markers of HIP1 and ANO4 correlated negatively (P < 0.05) with clinical stone events and basement membrane calcifications on papillary tip biopsies., Conclusions: Urinary excretion of EVs derived from specific types of activated immune cells and EVs with proteins related to calcium/phosphorus regulation differed between CSFs and NSFs. Further validation of these and other populations of urinary EVs in larger cohort could identify biomarkers that elucidate novel pathogenic mechanisms of calcium stone formation in specific subsets of patients.

Background: In patients with secondary (autoimmune) membranous nephropathy, two novel proteins, Exostosin 1 and Exostosin 2 (EXT1/EXT2), are potential disease antigens, biomarkers, or both. In this study, we validate the EXT1/EXT2 findings in a large cohort of membranous lupus nephritis., Methods: We conducted a retrospective cohort study of patients with membranous lupus nephritis, and performed immunohistochemistry studies on the kidney biopsy specimens against EXT1 and EXT2. Clinicopathologic features and outcomes of EXT1/EXT2-positive versus EXT1/EXT2-negative patients were compared., Results: Our study cohort included 374 biopsy-proven membranous lupus nephritis cases, of which 122 (32.6%) were EXT1/EXT2-positive and 252 (67.4%) were EXT1/EXT2-negative. EXT1/EXT2-positive patients were significantly younger ( P =0.01), had significantly lower serum creatinine levels ( P =0.02), were significantly more likely to present with proteinuria ≥3.5 g/24 h ( P =0.009), and had significantly less chronicity features (glomerulosclerosis, P =0.001 or interstitial fibrosis and tubular atrophy, P <0.001) on kidney biopsy. Clinical follow-up data were available for 160 patients, of which 64 (40%) biopsy results were EXT1/EXT2-positive and 96 (60%) were EXT1/EXT2-negative. The proportion of patients with class 3/4 lupus nephritis coexisting with membranous lupus nephritis was not different between the EXT1/EXT2-positive and EXT1/EXT2-negative groups (25.0% versus 32.3%; P= 0.32). The patients who were EXT1/EXT2-negative evolved to ESKD faster and more frequently compared with EXT1/EXT2-positive patients (18.8% versus 3.1%; P =0.003)., Conclusions: The prevalence of EXT1/EXT2 positivity was 32.6% in our cohort of membranous lupus nephritis. Compared with EXT1/EXT2-negative membranous lupus nephritis, EXT1/EXT2-positive disease appears to represent a subgroup with favorable kidney biopsy findings with respect to chronicity indices. Cases of membranous lupus nephritis that are EXT1/EXT2-negative are more likely to progress to ESKD compared with those that are EXT1/EXT2-positive., (Copyright © 2021 by the American Society of Nephrology.)

Immunoglobulin light chain amyloidosis is the most frequent type of renal amyloidosis in the United States, accounting for 81% of cases. Accurate typing is crucial for early diagnosis and treatment of immunoglobulin-derived amyloidosis and to avoid treating other amyloidoses with potentially toxic chemotherapy. Immunofluorescence is the first step to type renal immunoglobulin-derived amyloidosis but the performance characteristics of this method are largely unknown. Here, we establish the sensitivity and specificity of immunofluorescence for diagnosing immunoglobulin-derived amyloidosis in patients whose amyloid typing was performed by the current gold standard of laser microdissection/mass spectrometry. Renal biopsy pathology reports originating from several institutions with a diagnosis of amyloidosis and which had amyloid typing by laser microdissection/mass spectrometry performed at our center were reviewed. Reported immunofluorescence staining for kappa or lambda of 2+ or more, with weak or no staining for the other light chain was considered positive for light chain amyloidosis by immunofluorescence. Based on microdissection/mass spectrometry results, of the 170 cases reviewed, 104 cases were typed as immunoglobulin-derived amyloidosis and 66 were typed as non-immunoglobulin-derived amyloidosis. Immunofluorescence sensitivity for diagnosing immunoglobulin-derived amyloidosis was 84.6%. The remaining 16 cases could not be diagnosed by immunofluorescence due to reported weak staining for all antigens or reported lack of preferential staining for one antigen. Immunofluorescence specificity was 92.4%. Five cases, all amyloid A amyloidosis, were misdiagnosed as immunoglobulin-derived amyloidosis by immunofluorescence. Immunofluorescence failed to accurately differentiate immunoglobulin-derived from non-immunoglobulin-derived amyloidosis in 12.3% of cases of renal amyloidosis. Relying on immunofluorescence alone for determining immunoglobulin-derived vs. non-immunoglobulin-derived amyloidosis may lead to misdiagnosis. Thus, immunofluorescence has inferior sensitivity and specificity compared with laser microdissection/mass spectrometry in the typing of immunoglobulin-derived amyloidosis., (Copyright © 2019 International Society of Nephrology. Published by Elsevier Inc. All rights reserved.)

Objectives: Albumin messenger RNA (mRNA) expression is a marker of hepatocellular differentiation. Most published data are from review of tissue microarrays, and albumin in situ hybridization (ISH) expression across several tumor types is incompletely characterized., Methods: Sections from 221 tumors were evaluated for albumin mRNA. Immunohistochemistry was used to confirm diagnoses. Albumin ISH was performed according to manufacturer-provided instructions. Fifty-nine cases were evaluated with both commercial ISH assays., Results: Albumin mRNA was detected in all hepatocellular carcinomas (HCCs) and 81% of intrahepatic cholangiocarcinomas. Lung (20%), gallbladder (39%), hepatoid pancreatic (n = 1 of 1) adenocarcinoma, breast invasive ductal carcinoma (18%), yolk sac tumor (25%), and acinar cell carcinoma (29%) showed expression. Both assays were concordant in 93% of cases., Conclusions: Albumin ISH was expressed in all HCCs studied. It was also positive in intrahepatic cholangiocarcinoma and patchy positive in gallbladder adenocarcinoma and a subset of other neoplasms, which can be a potential pitfall., (© American Society for Clinical Pathology, 2019. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

Rationale & Objective: Congo Red positivity with birefringence under polarized light has traditionally permitted classification of organized glomerular deposits as from amyloid or nonamyloid diseases. The absence of congophilia has been used to differentiate fibrillary glomerulonephritis (GN) from amyloidosis. We describe a series of fibrillary GN cases in which the deposits are Congo Red-positive (congophilic fibrillary GN) and discuss the role of DNAJB9 in distinguishing congophilic fibrillary GN from amyloidosis., Study Design: Case series., Setting & Participants: Analysis of the clinicopathologic characteristics of 18 cases of congophilic fibrillary GN. Mass spectrometry was performed and compared with 24 cases of Congo Red-negative fibrillary GN, 145 cases of amyloidosis, and 12 apparently healthy individuals. DNAJB9 immunohistochemistry was obtained for a subset of cases., Results: The proteomic signature of amyloid was not detected using mass spectrometry among cases of congophilic fibrillary GN. DNAJB9, a recently discovered proteomic marker for fibrillary GN, was detected using mass spectrometry in all cases of fibrillary GN regardless of congophilia and was absent in cases of amyloidosis and in healthy individuals. DNAJB9 immunohistochemistry confirmed the mass spectrometry findings. The congophilic fibrillary GN cases included 11 men and 7 women with a mean age at diagnosis of 65 years. Concomitant monoclonal gammopathy, hepatitis C virus infection, malignancy, or autoimmune disease was present in 35%, 22%, 17%, and 11% of patients, respectively. No patient had evidence of extrarenal amyloidosis. Patients presented with proteinuria (100%), nephrotic syndrome (47%), hematuria (78%), and chronic kidney disease (83%). After a mean follow-up of 23 months, 31% of patients progressed to end-stage kidney disease and the remaining 69% had persistently reduced kidney function., Limitations: Retrospective nature. Blinded pathology evaluations were not performed., Conclusions: The congophilic properties of organized fibrillary deposits should not be solely relied on in differentiating fibrillary GN from renal amyloidosis. Mass spectrometry and DNAJB9 immunohistochemistry can be useful in making this distinction., (Copyright © 2018 National Kidney Foundation, Inc. Published by Elsevier Inc. All rights reserved.)

Introduction: Fibrillary glomerulonephritis (FGN) is a rare disease with unknown pathogenesis and a poor prognosis. Until now, the diagnosis of this disease has required demonstration of glomerular deposition of randomly oriented fibrils by electron microscopy that are Congo red negative and stain with antisera to Igs. We recently discovered a novel proteomic tissue biomarker for FGN, namely, DNAJB9., Methods: In this work, we developed DNAJB9 immunohistochemistry and tested its sensitivity and specificity for the diagnosis of FGN. This testing was performed on renal biopsy samples from patients with FGN (n = 84), amyloidosis (n = 21), a wide variety of non-FGN glomerular diseases (n = 98), and healthy subjects (n = 11). We also performed immunoelectron microscopy to determine whether DNAJB9 is localized to FGN fibrils., Results: Strong, homogeneous, smudgy DNAJB9 staining of glomerular deposits was seen in all but 2 cases of FGN. The 2 cases that did not stain for DNAJB9 were unique, as they had glomerular staining for IgG only (without κ or λ) on immunofluorescence. DNAJB9 staining was not observed in cases of amyloidosis, in healthy subjects, or in non-FGN glomerular diseases (with the exception of very focal staining in 1 case of smoking-related glomerulopathy), indicating 98% sensitivity and > 99% specificity. Immunoelectron microscopy showed localization of DNAJB9 to FGN fibrils but not to amyloid fibrils or immunotactoid glomerulopathy microtubules., Conclusion: DNAJB9 immunohistochemistry is sensitive and specific for FGN. Incorporation of this novel immunohistochemical biomarker into clinical practice will now allow more rapid and accurate diagnosis of this disease.

In radical cystectomy specimens with bladder cancer, lymphatic and vascular invasion are often reported as 'angiolymphatic' or 'lymphovascular' invasion, terms that combine the findings of tumour within simple endothelial-lined lymphatic spaces and tumour within muscle-lined blood vessels. It is unclear if these patterns of invasion have different prognostic significance. In addition, there are conflicting data regarding the significance of lymphatic, vascular and perineural invasion in patients with bladder cancer. Herein, we studied 1504 patients treated by radical cystectomy for bladder cancer at our institution and followed for a mean of 10.6 years. Cases were re-reviewed by a urological pathologist for lymphatic invasion defined as tumour within a non-muscle-lined endothelial-lined lymphatic space, vascular invasion defined as tumour in a muscle-lined blood vessel, and perineural invasion defined as tumour within the perineural sheath. Associations of clinical and pathological features with bladder cancer death were evaluated using Cox proportional hazards regression models and summarised with hazard ratios and 95% confidence intervals. Survival was estimated by the Kaplan-Meier method. Multivariate analysis showed that lymphatic and vascular invasion but not perineural invasion were significantly associated with cancer specific survival (p<0.0001 and p=0.02, respectively). There was a significant association of lymphatic and vascular invasion but not perineural invasion with involved regional lymph nodes (p<0.0001 and p=0.004, respectively). In patients with metastasis to regional lymph nodes, lymphatic invasion remained significantly associated with outcome (p=0.02). The frequency of lymphatic and vascular invasion varied amongst histological subtypes of bladder cancer. Vascular and lymphatic invasion should be clearly defined and reported for radical cystectomy specimens containing bladder cancer., (Copyright © 2017 Royal College of Pathologists of Australasia. Published by Elsevier B.V. All rights reserved.)

Chronic changes represent an important component of native kidney biopsy evaluation and have a major bearing on predicting prognosis and guiding treatment. We propose here a uniform, semiquantitative approach to assessing such changes, which include glomerulosclerosis, tubular atrophy, interstitial fibrosis, and arteriosclerosis, and we report these findings as an overall chronicity grade., (Copyright © 2017 International Society of Nephrology. Published by Elsevier Inc. All rights reserved.)

Objective: To study the prevalence of, risk factors for, and renal functional consequences of ductal plug formation in idiopathic calcium oxalate (iCaOx) stone formers (SF)., Patients and Methods: Accessible renal papillae were videotaped to determine the percent surface area (SA) occupied by plaque and ductal plug in a consecutive cohort of iCaOx SF undergoing percutaneous nephrolithotomy for stone removal., Results: Between 2009 and 2014, iCaOx SF comprised 96 of 240 enrolled patients. Of these, 41 (43%) had ductal plugs. Mean plaque SA did not differ between the low and high % plug groups (2.1% vs 3.4%, respectively). The amounts of mean % SA plaque and ductal plug were not strongly correlated (Spearman's ρ = 0.12, P = .3). Patients with >1% mean SA plug had a higher urinary pH (median 6.5 vs 6.0, P = .02) and elevated urinary hydroxyapatite supersaturation (median 5.4 vs 3.7 delta G; P = .04). Those with >1% plugging had more extensive ductal dilation (P = .002) compared to those with ≤1%. However, estimated glomerular filtration rate was the same (median 75.4 mL/min/1.73 m(2) vs 74.7 mL/min/1.73 m(2)). Number of prior stone events was associated with mean and maximum papillary SA occupied by plug (P < .05 for both), but not plaque (P = .3 and p = .5, respectively)., Conclusion: Within a cohort of iCaOx SF, macroscopic plaque and ductal plugs often coexist. Intraluminal features known to favor calcium phosphate crystallization appear to play a role in plug formation. The pathogenic significance of these plugs remains to be established, although their extent appears to correlate with stone burden., (Copyright © 2016 Elsevier Inc. All rights reserved.)

Polyomavirus nephropathy is characterized histopathologically by evidence of viral replication and acute tubular injury with interstitial inflammation, tubulitis, and intranuclear inclusions. Polyomavirus nephropathy typically develops in the kidney transplant as a combination of the unique nature of the transplanted tissue and the immunomodulated status of the patient. We present a case in which a patient had lingering BK viremia and declining kidney function following receipt of lung and kidney transplants. A kidney biopsy was performed, which demonstrated BK polyomavirus tubulointerstitial nephritis, resultant cytopathic changes and tubular/ductal injury, associated urothelial hyperplasia with foci of squamous metaplasia, suspected membranous glomerulopathy, and moderate arterial/arteriolar sclerosis. There was also evidence of more proximal nephron viral involvement, with glomerular parietal epithelium infection and injury present. This case shows impressive BK polyomavirus-associated urothelial hyperplasia in the kidney, which to our knowledge has not been previously illustrated in the literature. There have been numerous studies attempting to show the association of polyomaviruses with the development of carcinoma, and this case report is significant because it is an example of viral-induced changes that are concerning and hold potential for malignant transformation., (Copyright © 2016 National Kidney Foundation, Inc. Published by Elsevier Inc. All rights reserved.)

C3 glomerulonephritis (C3GN) results from genetic or acquired dysregulation of the alternative complement pathway. A subset of patients may have clinical and biochemical characteristics compatible with an autoimmune disorder. We studied a cohort of 85 patients with confirmed C3GN (2007-2014), of which ten patients (3 male, 7 female; mean age 38.5 years) had an associated autoimmune disorder. All patients had abnormal ANA titers, 6 also had positive ds-DNA titers. At the time of presentation with C3GN, all 7 female patients had autoimmune-related presentations. Of the 3 male patients, only 1 patient had autoimmune-related presentations. Kidney biopsy showed predominantly mesangial proliferative or membranoproliferative glomerulonephritis. In 5 patients, the alternative pathway was evaluated. All had allele variants/polymorphisms associated with C3GN. One patient was also positive for C3Nefs. Treatment varied form conservative management to the use of prednisone alone or with cytotoxic therapy. Mean serum creatinine decreased from 2.0 to 1.4 mg/dL while proteinuria decreased from 2300 to 994 mg/24 h in 8 patients with follow-up. The study highlights the association between C3GN and autoimmune disorders, particularly in female patients. The study suggests that an autoimmune milieu may act as a trigger for the development of C3GN in genetically susceptible patients. Short-term prognosis of C3GN associated with autoimmune disorders appears excellent.

Objective: To describe the endoscopic characteristics of renal papillae in struvite stone formers (SFs)., Materials and Methods: From 2009 to 2014, patients undergoing percutaneous nephrolithotomy were prospectively enrolled in our study. Endoscopic analysis and biopsy of papillae were performed to demonstrate the presence and percentage surface area (SA) of Randall's plaque or ductal plug. Comparison with idiopathic calcium oxalate (CaOx) SF and non-SF controls was performed., Results: We identified 29 struvite SFs to compare with 90 idiopathic CaOx SFs and 17 controls. On endoscopic mapping, 28 struvite SFs (97%) demonstrated Randall's plaque and 9 (31%) had plugging. The average mean SA of Randall's plaque in struvite SF (1.5 ± 1.4%) was less than CaOx SFs (3.7 ± 4.3%, P  =  .0018) and similar to controls (1.7 ± 2.7%, P  =  .76). Average mean plug SA was similar between struvite SFs, CaOx SFs, and controls. On metabolic assessment, 83% of struvite SFs had at least one urine abnormality, with urinary uric acid and oxalate levels significantly higher among struvite SFs compared to controls (P  =  .002). Despite lack of active urinary tract infection, interstitial inflammation was more prevalent in struvite SFs compared to CaOx SFs (43.5% vs 7.3%, P  =  .0001)., Conclusions: Our findings suggest a limited role for Randall's plaque in struvite stone formation. Struvite SFs have less plaque formation than CaOx SFs, but demonstrate evidence of severe parenchymal inflammation compared to other SFs. The role of this prominent interstitial inflammation requires further study., (Copyright © 2016 Elsevier Inc. All rights reserved.)

Anti-glomerular basement membrane (anti-GBM) disease is a major cause of rapidly progressive glomerulonephritis (RPGN). On the other hand, fibrillary glomerulonephritis (GN) typically presents as proteinuria, hematuria and renal insufficiency, but rarely as RPGN. Without electron microscopy, the diagnosis of fibrillary GN can be missed. We report a 68-year-old white woman who presented with RPGN with kidney biopsy demonstrating diffuse crescentic GN on light microscopy. By immunofluorescence, there was bright linear staining of the GBMs and smudgy mesangial staining for immunoglobulin G, C3, and kappa and lambda light chain. Electron microscopy revealed fibrillary deposits in the GBM and mesangium. A serum test for anti-GBM antibody was positive. To our knowledge, this is the first report of coexistence of fibrillary GN in a patient with anti-GBM disease. Electron microscopy is critical to identify the coexistence of other GN in patients presenting with crescentic GN.

Objective: To characterize the endoscopic and histologic renal papillary lesions in a cohort of uric acid (UA) stone formers (SF)., Methods: Data were prospectively obtained during percutaneous nephrolithotomy between 2009 and 2013. Renal papillae were endoscopically analyzed to quantitate surface area occupied by plaque or plug, and biopsies were obtained. UA SF were compared with non-SF controls and patients with >50% calcium oxalate (CaOx) in the absence of UA., Results: There were 23 UA SF; of which 19 stones (83%) were admixed with CaOx and 4 (17%) were pure. Compared with CaOx SF and controls, UA SF had a higher prevalence of diabetes and obesity, greater serum creatinine and UA levels, lower estimated glomerular filtration rate and urine pH, and elevated UA supersaturation. Characteristics of UA SF were compared with 95 CaOx SF and 19 controls. Overall, 23 (100%) UA SF had endoscopic plaque and 13 (57%) plugs. Endoscopically, UA SF displayed a greater incidence of plugging (57% vs 45% vs 11%; P = .006) relative to CaOx SF and controls. Likewise, UA SF had a greater percentage surface area of plugging (0.1 vs 0.0; P = .002) and plaque (2.0 vs 0.9; P = .006) than controls but similar amounts to CaOx SF. Histologic plugs were similar in UA and CaOx SF, although CaOx SF demonstrated greater interstitial inflammation on endoscopic biopsy., Conclusion: UA and CaOx SF have similar amounts of plaque, whereas UA SF have more endoscopic but not histologic collecting duct plugs. These data suggest an overlap between the pathogenesis of UA and CaOx stones. The anchoring site for UA stones remains uncertain., (Copyright © 2015 Elsevier Inc. All rights reserved.)

Background: Overgrowth of calcium oxalate on Randall's plaque is a mechanism of stone formation among idiopathic calcium oxalate stone-formers (ICSFs). It is less clear how stones form when there is little or no plaque., Design, Setting, Participants, & Measurements: Participants were a consecutive cohort of ICSFs who underwent percutaneous nephroscopic papillary mapping in the kidney or kidneys containing symptomatic stones and a papillary tip biopsy from a representative calyx during a stone removal procedure between 2009 and 2013. The distribution of Randall's plaque coverage was analyzed and used to divide ICSFs into those with a high (≥5%; mean, 10.5%; n=10) versus low (<5%; mean, 1.5%; n=32) amount of plaque coverage per papilla. Demographic and laboratory features were compared between these two groups., Results: Low-plaque stone formers tended to be obese (50% versus 10%; P=0.03) and have a history of urinary tract infection (34% versus 0%; P=0.04). They were less likely to have multiple prior stone events (22% versus 80%; P=0.002) and had a lower mean 24-hour urine calcium excretion (187±86 mg versus 291±99 mg; P<0.01). Morphologically, stones from patients with low amounts of plaque lacked a calcium phosphate core by microcomputed tomography. Papillary biopsies from low plaque stone-formers revealed less interstitial and basement membrane punctate crystallization., Conclusions: These findings suggest that other pathways independent of Randall's plaque may contribute to stone pathogenesis among a subgroup of ICSFs who harbor low amounts of plaque., (Copyright © 2014 by the American Society of Nephrology.)