Introduction: Membranoproliferative glomerulonephritis is a pattern of glomerular injury on renal biopsy with characteristic light microscopic changes, namely mesangial hypercellularity, endocapillary proliferation and double contour formation along the glomerular capillary walls. This pattern does not represent a disease per se but can occur as a result of different pathologic processes. Case Presentation: We present a case of a 37-year-old caucasian female patient with thrombotic microangiopathy (TMA), severe hypertension and immune-complex-mediated glomerulonephritis, secondary to hepatitis C virus (HCV) infection. Steroid therapy and fresh-frozen plasma infusions were started, with progressive improvement of lab results. Treatment of HCV infection was started with direct-acting antiviral therapy. The results of the genetic study of the complement alternative pathway regulatory proteins were positive for a homozygote variant of the gene CFHR5 (p.Val110Ala) and a homozygote deletion on CFHR3/CFHR1 proteins. Discussion: Hypertension is commonly associated with TMA and could explain the features of this case. Nevertheless, the differential diagnosis is often difficult because TMA caused by hypertension is indistinguishable from all other entities. The finding of a homozygote variant of the gene CFHR5, and a homozygote deletion on CFHR3/CFHR1 proteins, raised the possibility that this case might have been an Atypical Hemolytic Uremic Syndrome (aHUS) triggered by the endothelial damage caused by the HCV-related cryoglobulinemic glomerulonephritis

RESUMO Tumor fibroso solitário (TFS) é uma neoplasia mesenquimatosa rara composta por células fusiformes monótonas, intercaladas por fibras de colágeno. Localização renal é incomum, com escassos casos descritos. Relatamos dois casos do gênero masculino, com 40 e 48 anos, um com detecção incidental de massa periférica; outro com lesão hilar descoberta na sequência de investigação por hematúria. Ambos revelaram proliferação fusocelular sem mitoses nem necrose. Imuno-histoquímica: positividade para CD34, CD99 e linfoma de células B2 (Bcl-2). Não há evidência de recidiva nove e cinco meses após cirurgia, respetivamente. TFS é maioritariamente benigno, mas pode revelar comportamento agressivo. Características morfológicas e imuno-histoquímicas são essenciais para o diagnóstico.

ABSTRACT Solitary fibrous tumor (SFT) is a rare mesenchymal neoplasm, composed of monotonous spindle cells, intermingled with collagen fibers. Kidney location is sporadic, with few reports in literature. We present two cases of 40- and 48-year-old males, one with incidental detection of a peripheral mass; another with hilar lesion perceived following investigation of hematuria. Both revealed a spindle-cell proliferation, without mitosis and necrosis. Immunohistochemical studies: positivity for CD34, CD99 and B-cell lymphoma 2 (Bcl-2). No sign of disease were evident nine and five months after surgery, respectively. SFT is mostly benign, but can show malignant behavior. Morphologic and immunohistochemical characteristics are essential for diagnosis.

RESUMEN Tumor fibroso solitario (TFS) es una neoplasia mesenquimal infrecuente de células fusiformes monótonas, separadas por bandas de colágeno. Localización renal es poco habitual, con escasos casos descriptos. Reportamos dos casos de pacientes masculinos, de 40 e 48 anos, el uno con detección incidental de masaperiférica; el otro con lesión hiliar descubierta en la investigación de hematuria. Los dos revelaronproliferación fusocelular sin necrosis ni mitosis. Inmunohistoquímica: positividad para CD34, CD99 y linfoma de células B2 (Bcl-2). No hay evidencia de recidiva a los nueve y cinco meses de la cirugía, respectivamente. TFS es, por lo general, benigno, pero puede revelar comportamiento agresivo. Características morfológicas y inmunohistoquímicas son esencialespara el diagnóstico.

RESUMO Nefroma quístico pediátrico é uma neoplasia de patogênese incerta caracterizada por uma arquitetura multilocular, que ocorre maioritariamente em crianças. Alguns casos podem ser esporádicos e outros podem apresentar associação familiar, juntamente com outras neoplasias, constituindo a síndrome DICER1. Apresentamos o caso de um nefroma quístico pediátrico com uma mutação do gene DICER1 não reportada na literatura e exploramos o diagnóstico diferencial, principalmente com o nefroblastoma quístico parcialmente diferenciado.

ABSTRACT Paediatric cystic nephroma is a neoplasm of uncertain pathogenesis characterized by a multilocular architecture that develops in children. Some cases may be sporadic, and others may present a familial association, together with other neoplasms, as part of a DICER1 syndrome. We present a case of a paediatric cystic nephroma with an unreported DICER1 mutation and explore the differential diagnosis mainly with cystic partially differentiated nephroblastoma.

C3 Glomerulopathy is a rare disease caused by abnormal control of the alternative complement pathway, resulting in a predominant glomerular C3 deposition. Its association with multiple myeloma has been reported in recent literature. We present a case of a 66-year-old women, referred for a nephrology consultation with a stage 4 chronic kidney disease, microhematuria, leukocyturia, sub-nephrotic range proteinuria (1.3 g/24hours), albumin 3.7 g/dl and dyslipidemia. She had been previously studied in a Hematology consultation for a normocytic anemia and an IgG Kappa monoclonal gammopathy, with 16% of plasma cells in bone marrow aspiration, but no hypercalcemia or lytic bone lesions. Autoimmune tests (ANCA, ANA, Anti-dsDNA antibody), C3 and C4 were negative. Eight months later, the patient complained of hypertension and edema, and presented a mild decrease in serum C3 (0.86 g/L [0.90-1.80]) and progressive nephrotic proteinuria (from 4.5 to 6.1 g/24h), with hypoalbuminemia. A kidney biopsy was performed, and we found mild chronic non-specific glomerular and tubule-interstitial findings, on light microscopy, and mesangial C3 deposits (+++), without immunoglobulin deposits, on immunofluorescence. Immunofluorescence with protease-digested paraffin sections was also negative. Genetic study found no complement gene mutation. She was treated with prednisone 1mg/Kg/day, with a favorable clinical and laboratorial response, but whether this treatment is enough it is still being pondered between nephrologists and hematologists

RESUMO Carcinoma urotelial invasor da bexiga, variante plasmocitoide, é uma entidade rara, com poucos casos descritos na literatura. Relatamos o caso de um homem, 79 anos, submetido à resseção transvesical de tumor da bexiga, cuja histologia revelou carcinoma urotelial de alto grau pT1. Posteriormente, foi submetido à cistoprostatectomia radical, que mostrou carcinoma urotelial invasor, descoeso, de tipo plasmacitoide, positivo para citoqueratina 7 (CK7), citoqueratina 20 (CK20) e fator de transcrição de ação"trans" específico de células T (GATA-3) e negativo para E-caderina e CD138. É importante reconhecer a variante plasmocitoide do carcinoma urotelial invasor, uma vez que se evita potencial diagnóstico errado de doença metastática.

ABSTRACT Invasive bladder urothelial carcinoma, plasmacytoid variant is a rare entity with scarce cases reported in the literature. We report a case of a 79 years old male, subjected to transurethral resection of bladder tumor, which histological examination revealed a pT1 high-grade urothelial carcinoma. Subsequently, he underwent radical cystoprostatectomy, which showed urothelial carcinoma with lack of cohesion, plasmacytoid variant, positive for citokeratin 7 (CK7), citokeratin 20 (CK20) and trans-acting T-cell-specific transcription factor (GATA-3), and negative for E-cadherin and CD138. It is important to recognize the plasmacytoid variant of the invasive urothelial carcinoma, since it avoids a potential misdiagnosis of metastatic cancer.

O atingimento renal nas vasculites associadas aos anticorpos anticitoplasma de neutrófilo (ANCA) traduz-se, tipicamente, por uma glomerulonefrite crescentica pauci-imune. O achado de alguns depósitos de imunocomplexos nestas glomerulonefrites nao e incomum, mas os casos em que esta deposição e mais acentuada, sugerem a presença de uma segunda doença glomerular mediada por imunocomplexos. O significado dos depósitos de imunocomplexos e o seu papel nas vasculites associadas a ANCA e ainda um tema de debate, contudo, nestes doentes foram descritos niveis superiores de proteinuria e um pior prognostico em relação a preservação da função renal. Descrevemos o caso clinico de um doente com uma glomerulonefrite mesangioproliferativa em relação com uma crioglobulinemia mista secundaria a uma infeção cronica pelo vírus da hepatite C, que desenvolve posteriormente uma glomerulonefrite rapidamente progressiva associada a vasculite com ANCA anti-mieloperoxidase positivo.

Renal involvement of antineutrophil cytoplasmic antibodies (ANCA) associated vasculitis typically occurs in the form of a pauci-immune crescentic glomerulonephritis. The finding of some immune complex deposits in these glomerulonephritis is not unusual, but the cases with greater than mild deposition suggest the presence of a second and immune complex related glomerular disease. The significance of the immune complex deposits and their role in ANCA associated vasculitis is still a topic of debate, but higher levels of proteinuria and worse prognosis with respect to renal function have been described in these patients. We report a case of a patient with a known mesangial proliferative glomerulonephritis related to a mixed cryoglobulinemia secondary to a chronic hepatitis C infection that later developed a rapidly progressive glomerulonephritis due to a superimposed anti-myeloperoxidase ANCA positive glomerulonephritis.