Mayo Clinic/Renal Pathology Society Consensus Report on Pathologic Classification, Diagnosis, and Reporting of GN.

Renal pathologists and nephrologists met on February 20, 2015 to establish an etiology/pathogenesis-based system for classification and diagnosis of GN, with a major aim of standardizing the kidney biopsy report of GN. On the basis of etiology/pathogenesis, GN is classified into the following five pathogenic types, each with specific disease entities: immune-complex GN, pauci-immune GN, antiglomerular basement membrane GN, monoclonal Ig GN, and C3 glomerulopathy. The pathogenesis-based classification forms the basis of the kidney biopsy report. To standardize the report, the diagnosis consists of a primary diagnosis and a secondary diagnosis. The primary diagnosis should include the disease entity/pathogenic type (if disease entity is not known) followed in order by pattern of injury (mixed patterns may be present); score/grade/class for disease entities, such as IgA nephropathy, lupus nephritis, and ANCA GN; and additional features as detailed herein. A pattern diagnosis as the sole primary diagnosis is not recommended. Secondary diagnoses should be reported separately and include coexisting lesions that do not form the primary diagnosis. Guidelines for the report format, light microscopy, immunofluorescence microscopy, electron microscopy, and ancillary studies are also provided. In summary, this consensus report emphasizes a pathogenesis-based classification of GN and provides guidelines for the standardized reporting of GN.

The optimal number of biopsy fragments to establish a morphologic diagnosis of eosinophilic esophagitis.

OBJECTIVES: Eosinophilic esophagitis (EoE) is characterized clinically by dysphagia, chest pain, and food impaction, and morphologically by increased numbers of intraepithelial eosinophils and marked basal hyperplasia of the squamous mucosa. The consensus criteria for a diagnosis of EoE include the presence of ≥15 eosinophils/HPF in biopsies from both proximal and distal esophagus in the absence of other causes of esophageal eosinophilia, and the lack of clinical response to proton pump inhibitor therapy. Because of the variability in the distribution of intraepithelial eosinophils among biopsy fragments and the lack of standardized biopsy practices, we sought to determine the optimal number of esophageal biopsies from the mid and distal esophagus needed to reach the minimum morphologic criteria of ≥15 eosinophils/HPF. METHODS: From 5 January 2009 to 26 September 2011, 771 patients were diagnosed with EoE at our institution. From that patient population, 102 sequential cases were chosen for further study, all of whom had biopsies taken from the mid and distal esophagus. Cases with only gastric mucosa present and biopsies taken from patients with a previous diagnosis of EoE were excluded. The original H&E-stained slides were reviewed, and the number of biopsy fragments containing squamous mucosa was recorded. By using a × 40 objective and × 10 oculars (field diameter=0.52 mm, field area=0.21 mm(2)), the number of eosinophils per high power field (EOS/HPF) in up to three HPFs was counted in each biopsy fragment. RESULTS: The EOS/HPF were counted in 1,342 biopsy fragments. The number of biopsy fragments obtained from the mid esophagus ranged from 1 to 20 (mean 7; median 7) and those obtained from the distal esophagus ranged from 1 to 18 (mean 6; median 5). There was no significant difference between the mean number of EOS/HPF from the mid (26) and lower (25) esophagus or between the mean peak number of EOS/HPF from the mid (69.1) and lower (60.4) esophagus. The probability of one, four, five, and six biopsy fragments containing >15 EOS/HPF was 0.63, 0.98, 0.99, and >0.99, respectively. CONCLUSIONS: From these data, at least four biopsy fragments should be submitted from the mid and/or proximal esophagus to optimize the chances of a positive diagnosis of EoE in populations not known to have undergone previous proton pump inhibitor therapy. However, the yield is not increased beyond six biopsy fragments. In order to morphologically exclude a diagnosis of reflux esophagitis as the cause of intraepithelial eosinophilia, distal esophageal biopsies, if obtained, must be accompanied by more proximal biopsies (i.e., mid esophagus or higher).

Lymphocytic gastritis is not associated with active Helicobacter pylori infection.

BACKGROUND: Lymphocytic gastritis (LG), characterized by marked intra-epithelial lymphocytosis in the gastric mucosa, has been frequently associated with both celiac disease (CD) and H. pylori gastritis. The aim of this study was to review and correlate the morphology of LG with the presence of CD and H. pylori. MATERIALS AND METHODS: Gastric biopsies diagnosed with LG from 1/1/2006 to 8/1/2013 at our institution and corresponding small bowel biopsies, when available, were reviewed for verification of the diagnosis and to assess for the presence of H. pylori and CD. Immunohistochemical (IHC) staining for H. pylori was performed on all gastric biopsies. Demographic, clinical, and laboratory data were obtained from the medical record. RESULTS: Fifty-four of the 56 cases that met inclusion criteria demonstrated significant intra-epithelial lymphocytosis as the predominant histologic abnormality; however, none were associated with H. pylori infection by IHC staining. Two cases that also showed a prominent intra-epithelial and lamina propria neutrophilic infiltrate were both positive for H. pylori and were excluded from further study. Of the 36 small bowel biopsies available, 19 (53%) showed changes in CD. CONCLUSIONS: LG is not a distinct clinicopathologic entity, but a morphologic pattern of gastric injury that can be secondary to a variety of underlying etiologies. When restricted to cases with lymphocytosis alone, LG is strongly associated with CD and not with active H. pylori infection. However, cases that also show significant neutrophilic infiltrate should be regarded as "active chronic gastritis" and are often associated with H. pylori infection. A morphologic diagnosis of LG should prompt clinical and serologic workup to exclude underlying CD.

Frequency of metastasis to the gastrointestinal tract determined by endoscopy in a community-based gastroenterology practice.

Metastasis to the gastrointestinal tract is rare. We performed a retrospective analysis to identify patients with metastatic disease to the gastrointestinal tract using two databases containing pathology results from all endoscopic procedures conducted by nearly 200 gastroenterologists in a community setting over a 14-year period. Forty-nine patients were diagnosed with metastasis to the gastrointestinal tract by endoscopy during the study period. Most were women (71%). The most common metastases to the gastrointestinal tract identified by endoscopy were breast cancers (n = 18), followed by melanomas (n = 12), ovarian cancers (n = 7), kidney cancers (n = 5), prostate cancers (n = 2), lung cancer (n = 1), and pancreatic cancer (n = 1). Three patients had unknown primary sites. Among women, the three leading known primary tumor sites were breast, ovary, and melanoma. Among men, the three leading primary tumor sites were melanoma, kidney, and prostate. The stomach was the most common portion of the gastrointestinal tract involved by metastases. Most affected women and were most frequently encountered in the stomach.

Dense deposit disease associated with monoclonal gammopathy of undetermined significance.

Dense deposit disease (DDD) is a rare glomerular disease that typically affects children, young adults, and much less commonly, older patients. The pathophysiologic process underlying DDD is uncontrolled activation of the alternative pathway (AP) of complement cascade, most frequently secondary to an autoantibody to C3 convertase called C3 nephritic factor, although mutations in factor H and autoantibodies to this protein can impair its function and also cause DDD. Since 1995, we have diagnosed DDD in 14 patients aged 49 years or older; 10 of these patients (71.4%) carry a concomitant diagnosis of monoclonal gammopathy of undetermined significance (MGUS). In 1 of these 10 patients, the index case described here, we evaluated the AP and showed low serum AP protein levels consistent with complement activity, heterozygosity for the H402 allele of factor H, and low levels of factor H autoantibodies, which can affect the ability of factor H to regulate AP activity. In aggregate, these findings suggest that in some adults with MGUS, DDD may develop as a result of autoantibodies to factor H (or other complement proteins) that on a permissive genetic background (the H402 allele of factor H) lead to dysregulation of the AP with subsequent glomerular damage. Thus, DDD in some older patients may be a distinct clinicopathologic entity that represents an uncommon complication of MGUS.

Renal failure due to combined cast nephropathy, amyloidosis and light-chain deposition disease.

Renal dysfunction commonly occurs in multiple myeloma (MM) and is caused by deposition of abnormal light chain within various compartments of the kidney. Renal pathologic findings are diverse and include cast nephropathy (CN), amyloidosis and light-chain deposition disease (LCDD). We report a case of renal failure in a patient with MM caused by concurrent CN, amyloidosis and LCDD which has not been previously described.

Diagnosis and typing of systemic amyloidosis: The role of abdominal fat pad fine needle aspiration biopsy.

INTRODUCTION: Systemic amyloidosis (SA) has a broad nonspecific clinical presentation. Its diagnosis depends on identifying amyloid in tissues. Abdominal fat pad fine needle aspiration (FPFNA) has been suggested as a sensitive and specific test for diagnosing SA. MATERIALS AND METHODS: Thirty-nine FPFNA from 38 patients (16 women and 20 men, age range 40-88 years) during a 15-year period were reviewed. Smears and cell blocks were stained with Congo red (CR). A panel of antibodies (serum amyloid protein, serum amyloid A, albumin, transthyretin, kappa light chain and lambda light chain) was used on six cell blocks from five patients. The FNA findings were correlated with clinical and histological follow-up. RESULTS: FPFNAs were positive, confirmed by CR in 5/39 (13%), suspicious in 1/39 (3%), negative in 28/39 (72%), and insufficient for diagnosis in 5/39 (13%) of cases. In all the positive cases, SA was confirmed within 2-16 weeks. Among the 28 negative cases, SA was diagnosed in 21, the rest were lost to follow-up. Among the insufficient cases, SA was diagnosed in four and one was lost to follow-up. Specificity was 100%, whereas sensitivity was 19%. SA typing using cell block sections was successful in three, un-interpretable in one, and negative in two cases. CONCLUSION: FPFNA for SA is not as good as previously reported. This may be due to different practice setting, level of experience, diagnostic technique, or absence of abdominal soft tissue involvement. A negative result of FPFNA does not exclude SA. Immune phenotyping of amyloid is possible on cell block.

Long-term outcome of kidney transplantation in patients with fibrillary glomerulonephritis or monoclonal gammopathy with fibrillary deposits.

To determine the outcome of kidney transplantation in patients with fibrillary glomerulonephritis (FGN), a rare glomerular disease, we followed 12 patients, 5 with FGN and 7 patients with monoclonal gammopathy and fibrillary deposits (MGFD), who underwent 15 kidney transplants since 1988 with a median follow-up of 52 months. Recurrent disease did not arise in any of the patients with FGN but developed in 5 patients with MGFD. Seven allografts failed: 1 in the FGN group and 6 in the MGFD group. Median allograft survival for patients with MGFD was 37 months but had not been reached in FGN patients. One patient with FGN had primary allograft failure secondary to graft thromboembolism. Three patients with MGFD were re-transplanted and one lost the second allograft to recurrent disease, but the other two died from hematological malignancy. Another patient was diagnosed with MPGN type III and did not have detectable fibrillary material 22 months after transplantation. One patient with MGFD had stable allograft function 6 months post-transplant but another, with recurrent disease, underwent peripheral blood stem cell transplantation and regained stable allograft function. Our study shows that kidney transplantation appears safe in patients with FGN with little risk of recurrence. However, patients with MGFD have a significant risk for disease recurrence. Whether the development of hematological malignancies following transplantation in this group is related to their original disease or was coincidental requires further studies.

BK virus-associated nephropathy in a patient with AIDS.

The BK virus is a ubiquitous member of the group of human polyoma viruses that commonly is reactivated in the setting of immunosuppression related to renal transplantation, which results in tubulointerstitial nephritis and allograft dysfunction. BK virus-associated nephropathy occurring in association with human immunodeficiency virus infection and acquired immunodeficiency syndrome (AIDS) was reported only rarely. We describe the case of a 43-year-old man with AIDS presenting with nonoliguric renal failure. The renal biopsy specimen showed tubulointerstitial nephritis and renal tubular cell changes consistent with BK viral inclusions. Results of in situ hybridization for BK viral DNA were positive and showed tubular cell intranuclear inclusions. To our knowledge, this represents the third case of AIDS-associated BK virus-associated nephropathy diagnosed by means of biopsy.

Bleeding complications after transcutaneous kidney biopsy in patients with systemic amyloidosis: single-center experience in 101 patients.

BACKGROUND: Bleeding is one of the most common complications after kidney biopsy. Amyloidosis is thought to be 1 of the risk factors, but this has not been confirmed in a large study. We performed this study to assess the risk of bleeding after kidney biopsy in patients with amyloidosis. STUDY DESIGN: Retrospective study. SETTINGS & PARTICIPANTS: 101 patients with and 188 patients without amyloidosis undergoing outpatient percutaneous kidney biopsy at a major medical center in the absence of abnormal partial thromboplastin time, prothrombin time international normalized ratio, or platelet count and/or uncontrolled hypertension. PREDICTOR: Clinical diagnosis of amyloidosis. OUTCOMES & MEASUREMENTS: Post-kidney biopsy bleeding confirmed by means of imaging. Bleeding was defined as major if it required blood transfusion, hospital admission, or other invasive procedures and minor if none of these interventions were needed. RESULTS: Post-kidney biopsy bleeding was observed in 9.9% of patients with amyloidosis and 10.6% of controls (P = 0.8). Bleeding was major in 4% of patients with amyloidosis and 2.1% of controls (P = 0.4). Three patients from each group required blood transfusions and selective renal angiography. All except 1 patient from the control group underwent embolization. LIMITATIONS: Retrospective data analysis and overall low event rate did not allow for independent risk-factor analysis. CONCLUSIONS: The present study suggests that in the absence of a hematostatic disorder and/or uncontrolled hypertension, bleeding risk during kidney biopsy is not increased in patients with systemic amyloidosis. Kidney biopsy can be performed safely using the same screening criteria as for patients without amyloidosis.

Induction of heme oxygenase-1 and ferritin in the kidney in warm antibody hemolytic anemia.

Warm antibody autoimmune hemolytic anemia usually is associated with extravascular hemolysis. We report a case of a 42-year-old man with sustained and moderately severe warm antibody autoimmune hemolytic anemia, hemoglobinuria, hemosiderinuria, and acute kidney injury. We show marked induction of heme oxygenase-1 and increased ferritin expression in renal tubules, along with increased iron deposition in renal proximal tubules. These findings in this clinical case thus recapitulate those observed in experimental models of heme protein-induced kidney injury in which a coupled induction of heme oxygenase-1 and ferritin occurs in the kidney. We discuss the pathobiological significance of these findings and suggest that this linked response confers cytoprotection to the kidney exposed to hemoglobin and mitigates the severity of acute kidney injury that may otherwise occur. Finally, this case report documents that nephrotic-range proteinuria can occur in patients with autoimmune hemolytic anemia complicated by hemoglobinuria.

Nodular glomerulosclerosis: renal lesions in chronic smokers mimic chronic thrombotic microangiopathy and hypertensive lesions.

Cigarette smoking is associated with vascular lesions and chronic renal failure. In this report, we describe clinical and kidney biopsy findings for a 66-year-old woman with a history of long-term heavy cigarette smoking who developed proteinuria and decreasing renal function. This study also describes clinical and kidney biopsy findings for 9 patients with a history of smoking. None of these patients had hypertension, diabetes mellitus, or other risk factors that might result in vascular injury. Renal biopsy specimens showed a range of long-term changes with varying degrees of focal segmental or focal global glomerulosclerosis, nodular glomerulosclerosis, ischemic glomeruli, interstitial fibrosis and tubular atrophy, and mild to moderate arterial sclerosis and arteriolar hyalinosis. Electron microscopy often showed glomerular capillary wall thickening caused by subendothelial expansion by cellular elements and new basement formation resulting in segments of double contours. These changes indicate endothelial injury and glomerular capillary wall remodeling; the lesions mimic those seen in patients with chronic hypertension and chronic or healed thrombotic microangiopathies.

Malignant mixed epithelial and stromal tumor of the kidney with rhabdoid features: report of a case including immunohistochemical, molecular genetic studies and comparison to morphologically similar renal tumors.

Mixed epithelial stromal tumor of the kidney (MEST)/adult cystic nephroma (CN) is a lesion characterized by epithelial lined tubular or cystic structures interspersed within a variably prominent, distinctive spindle-cell stroma. Although typically benign, cases with malignant features have been reported. Herein, we report a MEST/CN with malignant stromal features and rhabdoid differentiation arising in the left kidney of an 84-year-old woman. Histologically, the tumor displayed multiple tubules and variably sized cystic structures lined by benign epithelium with an intervening malignant-appearing spindle-cell stroma. The malignant stroma displayed condensation in the regions surrounding the epithelial component consistent with the ovarian-like stroma typically observed in MEST/CN. In addition, the stromal cells displayed extensive rhabdoid differentiation. Immunohistochemical analysis revealed strong expression of cytokeratin 7, CAM 5.2, AE1/AE3, wide-spectrum keratin, and epithelial membrane antigen by the epithelial component. The stromal component displayed strong immunohistochemical expression of WT-1, CD-99, CD-56, INI1, and estrogen receptor; focal actin positivity; and was negative for desmin, myogenin, and progesterone receptor. Analysis by reverse transcriptase polymerase chain reaction failed to identify the SYT-SSX1 or SYT-SSX2 fusion transcripts characteristic of synovial sarcoma. To our knowledge, this represents the first report in the literature of malignant MEST with rhabdoid features and suggests that this entity should be considered in the diagnosis of renal stromal malignancies with prominent rhabdoid features.

A proliferative glomerulonephritis secondary to a monoclonal IgA.

A distinct entity mimicking immune-complex-mediated glomerulonephritis characterized by a proliferative glomerulonephritis with monoclonal immunoglobulin G (IgG) deposits recently was described. We now report a case of a 35-year-old woman who presented with sudden onset of edema, proteinuria, hematuria, and hypertension. Renal biopsy showed diffuse endocapillary proliferation, mesangial cellularity, and amorphous material in the mesangium. Immunofluorescence examination showed mesangial and capillary wall staining for IgA (2+), C3 (2+), fibrinogen (2+), and lambda (2+). Congo red stain was negative. Electron microscopy showed mesangial and subendothelial deposits with a paracrystalline lattice-like substructure forming parallel linear arrays. Extensive laboratory evaluation showed a small population of monoclonal plasma cells with lambda restriction. The present case suggests that monoclonal IgA deposits also can cause proliferative glomerulonephritis. However, the presence of paracrystalline deposits in association with monoclonal IgA deposits has not been described previously.

Anti-glomerular basement membrane glomerulonephritis: a morphologic study of 80 cases.

Anti-glomerular basement membrane (anti-GBM) glomerulonephritis is a rare disease caused by IgG autoantibodies against the glomerular basement membrane. We describe clinical and pathologic findings in a series of renal biopsy specimens from 80 patients. The patients ranged in age from 16 to 87 years. The age distribution was bimodal, with one peak at a young age predominated by males and a second peak in the sixth to eighth decades with females predominating. Most patients (70 [88%]) had severe necrotizing glomerulonephritis with crescents in more that 50% of glomeruli. The fraction of crescentic glomeruli in biopsy specimens correlated well with serum creatinine levels but not with serologic titers for anti-GBM antibodies. Interstitial fibrosis was uncommon and, when present, minimal to mild. Linear IgG deposition defines this entity, but immunofluorescent costaining for other immunoglobulins and complement is found frequently. To our knowledge, this is the largest series of renal biopsy specimens with anti-GBM glomerulonephritis studied to date.

A Comparison of splenectomy versus intensive posttransplant antidonor blood group antibody monitoring without splenectomy in ABO-incompatible kidney transplantation.

BACKGROUND: Although most protocols for ABO-incompatible kidney transplantation have employed splenectomy, its utility is unproven. The aim of the current study was to compare the outcomes of ABO-incompatible living donor kidney transplantation with splenectomy versus a protocol involving intensive posttransplant antibody monitoring to maintain low levels of antiblood group antibody. METHODS: We retrospectively studied all ABO-incompatible living donor kidney transplants at our institution between September 1999 and November 2004 (n=34). Prior to May 2003, all patients were included in a protocol involving pretransplant plasmapheresis and splenectomy at the time of transplant (n=23). After May 2003, splenectomy was not performed and a protocol that involved pretransplant anti-CD20 antibody and a more intensive posttransplant plasmapheresis regiment aimed at maintaining low levels of antiblood group antibody during the first 2 weeks following transplantation was utilized (n=11). RESULTS: Patient and graft survival was similar in the two groups. Humoral rejection occurred in 18% nonsplenectomized and 30% of splenectomized patients (P=0.68). Humoral rejection correlated with the baseline antibody titer in both groups. Individuals with elevated baseline antibody titer (> or =1:256) appear to be at high risk for humoral rejection regardless of protocol used. Antiblood group antibody levels 3 and 12 months after transplantation were similar in both groups. CONCLUSIONS: Splenectomy is not essential for successful ABO-incompatible kidney transplantation, although individuals with high baseline antidonor blood group antibody titers are at high risk for humoral rejection. The use of intensive posttransplant monitoring may help prevent antibody-mediated graft damage.

Recurrent Goodpasture's disease secondary to a monoclonal IgA1-kappa antibody autoreactive with the alpha1/alpha2 chains of type IV collagen.

Goodpasture's disease is characterized by crescentic glomerulonephritis and lung hemorrhage in the presence of anti-glomerular basement membrane (anti-GBM) antibodies. This disease usually is mediated by IgG autoantibodies directed against the noncollagenous domain of the alpha3(IV) collagen chain, the Goodpasture autoantigen. In rare cases, anti-GBM antibodies of IgA or IgM class are involved, but their specificity has not been determined, and their target antigen remains unknown. The authors present the case of a 62-year-old man with anti-GBM disease mediated by a monoclonal IgA-kappa antibody, which progressed to end-stage renal disease despite intensive immunosuppression. The patient underwent living-related kidney transplantation, but lung hemorrhage and crescentic glomerulonephritis recurred, causing the loss of the allograft 2 years later. Indirect immunofluorescence found the presence of circulating IgA antibodies reactive with a basement membrane component, identified by enzyme-linked immunoabsorbent assay and Western blot as the alpha1/alpha2(IV) collagen chains. Sensitivity to digestion with collagenase indicated that IgA bound to epitopes located in the collagenous domain. This is the first case of recurrent Goodpasture's disease secondary to an autoreactive IgA antibody. The specificity of an IgA antibody implicated in the pathogenesis of anti-GBM disease has been investigated for the first time, identifying the alpha1/alpha2(IV) collagen chains as a novel target for nephritogenic antibodies.

ABO-incompatible kidney transplantation using both A2 and non-A2 living donors.

BACKGROUND: Given the scarcity of cadaveric organs, efforts are intensifying to increase the availability of living donors. The current study assessed the feasibility of using ABO-incompatible living-donor kidneys to expand the donor pool. METHODS: The authors performed 18 ABO-incompatible living-donor kidney transplants between May 1999 and April 2001. Ten patients received living-donor kidneys from A2 and eight patients received kidneys from non-A2 blood group donors. Immunosuppression consisted of Thymoglobulin antibody induction, tacrolimus, mycophenolate mofetil, and prednisone. Eight non-A2 and two A2 kidney recipients also received a pretransplant conditioning regimen of four plasmapheresis treatments followed by intravenous immunoglobulin and splenectomy at the time of transplantation. Antidonor blood group antibody titer was measured at baseline, pretransplant, at 1- to 3-month and 1-year follow-up, and at the time of diagnosis of antibody-mediated rejection. RESULTS: No hyperacute rejection episodes occurred. One-year graft and patient survival rates in the 18 ABO-incompatible recipients were only slightly lower than those of 81 patients who received ABO-compatible kidney transplants during the same period (89% vs. 96% and 94% vs. 99%, respectively). Glomerular filtration rate and serum creatinine levels did not differ between the groups. Antibody-mediated rejection occurred in 28% of ABO-incompatible recipients, and was reversible with plasmapheresis, intravenous immunoglobulin, and increasing immunosuppression in all patients except one. CONCLUSIONS: ABO-incompatible living donor kidney transplants can achieve an acceptable 1-year graft survival rate using an immunosuppressive regimen consisting of Thymoglobulin induction, tacrolimus, mycophenolate mofetil, and prednisone combined with pretransplant plasmapheresis, intravenous immunoglobulin, and splenectomy.