Paraneoplastic pemphigus uncovers distinct clinical and biological phenotypes of western unicentric Castleman disease.

Unicentric Castleman disease (UCD) is a lymphoproliferative disease of unknown cause. Paraneoplastic pemphigus (PNP) is a major complication shown to be associated with a poor prognosis, with particular severity in patients with bronchiolitis obliterans (BO). This study describes the clinical and biological characteristics of UCD-PNP patients in a large Western cohort. A total of 148 patients diagnosed with UCD were identified, including 14 patients with a defined PNP. PNP was significantly associated with myasthenia gravis (MG) and FDC sarcoma during follow-up (FDCS). PNP was also significantly associated with reduced survival. These data, together with a multivariate analysis by principal components, led to the identification of UCD-PNP as a group at risk of MG, FDCS and death. PDGFRB sequencing performed on UCD lesions from six patients found the gain-of-function p.N666S variant in two. Interestingly, both patients had hyaline-vascular UCD subtype, were in the UCD-PNP subgroup and had FDCS. Sera from 25 UCD-PNP patients and 6 PNP patients without UCD were tested for PNP-associated autoantibodies. Sera from UCD-PNP patients had a strong reactivity against the N-terminal domain of recombinant periplakin (rPPL, 82%) and showed reactivity against at least two domains of rPPL. These features were not found in patients with UCD alone or in the PNP group without UCD. These data indicate that UCD-PNP patients belong to a subgroup sharing strong clinical and biological identity that might help to decipher the different dynamics of UCD natural history.

[Castleman disease]. / La maladie de Castleman.

The term "Castleman disease" covers a variety of entities that have very different clinical, biological, pathological and physiopathological features. In this issue, we review the characteristics of the unicentric Castleman disease, of the HHV8 associated multicentric Castleman disease and the idiopathic multicentric Castleman disease associated or not with TAFRO syndrome ("thrombocytopenia, anasarca, fever, reticulin myelofibrosis and/or renal insufficiency, organomegaly"). We detail the differential diagnostics of these entities.

A massive open online course to teach undergraduate medical students in oncology: keys of success.

Massive Open Online Courses (MOOCs) are gaining popularity in education while classroom lectures are being deserted, especially after COVID-19 pandemic. Their added value in teaching undergraduate medical students remains to be confirmed. This study evaluated a MOOC devoted to undergraduate medical students in a blended oncology-teaching university program. It was the first to target undergraduate medical students in oncology at its beginning. Students were asked to participate in a survey before and after MOOC to explore interactions between their characteristics and final grades, 65% of the participating students belonged to the rich class. 70% of the students completed the MOOC. Grades distributions were similar before and after MOOC implementation, so MOOC doesn't alter overall results. In addition, there was a positive effect of the MOOC on median grades on the immediate test. The univariate and multivariate analysis showed that socioeconomic status and student's willingness to participate interacted significantly with final results. Particularly, students' motivation and satisfaction were associated with better results; Almost 70% of students asked for blended learning. E-learning is reliable to teach oncology to undergraduate medical students. The success is directly linked to students' willingness to participate, and can be improved using blended methods including tutorials.

Dramatic Response After Switching MEK Inhibitors in a Patient With Refractory Mixed Histiocytosis.

We report the case of a patient with progressive multisystem mixed histiocytosis associating Langerhans cell histiocytosis (LCH) and Erdheim-Chester disease (ECD) involving the bone marrow, whose lesions harbored the MAP2K1 E102-I103del. After initial improvement under the MEK inhibitor trametinib, the treatment was only partially efficient and poorly tolerated. Eventually, although the trough blood level of trametinib at steady state was within expected ranges, the disease progressed to a life-threatening situation, with peritoneal involvement and anasarca. Switching to the MEK inhibitor cobimetinib as a salvage therapy resulted in a dramatic, rapid disease response, and the patient remains disease-free 3 years later with the treatment. The load of the MAP2K1 deletion in peripheral blood was correlated with the disease activity and strongly declined with cobimetinib, although it remained detectable at the last follow-up.

A Comprehensive Clinicopathologic and Molecular Study of 19 Primary Effusion Lymphomas in HIV-infected Patients.

Primary effusion lymphoma (PEL) is associated with human herpesvirus 8 and frequently with Epstein-Barr virus (EBV). We report here a single-center series of 19 human immunodeficiency virus-associated PELs, including 14 EBV+ and 5 EBV- PELs. The objectives were to describe the clinicopathologic features of PELs, with a focus on programmed cell death protein 1 (PD-1)/programmed death-ligand 1 (PD-L1) expression, to search for genetic alterations by targeted deep sequencing analysis, and to compare the features between EBV+ and EBV- cases. All the patients were male, and the median age at diagnosis was 47 years old (interquartile range: 40 to 56 y). Reflecting the terminal B-cell differentiation, immunophenotypic profiles showed low expression levels of B-cell markers, including CD19 (0/19), CD20 (1/19), CD79a (0/19), PAX5 (1/19), BOB1 (3/19), and OCT2 (4/19), contrasting with a common expression of CD38 (10/19), CD138 (7/19), and IRF4/MUM1 (18/19). We observed a frequent aberrant expression of T-cell markers, especially CD3 (10/19), and less frequently CD2 (2/19), CD4 (3/19), CD5 (1/19), and CD8 (0/19). Only 2 cases were PD-L1 positive on tumor cells and none PD-1 positive. With respect to immune cells, 3 samples tested positive for PD-L1 and 5 for PD-1. Our 36-gene lymphopanel revealed 7 distinct variants in 5/10 PELs, with either a single or 2 mutations per sample: B2M (n=2), CD58 (n=1), EP300 (n=1), TNFAIP3 (n=1), ARID1A (n=1), and TP53 (n=1). Finally, we did not observe any major clinical, pathologic, or immunohistochemical differences between EBV+ and EBV- PELs and the outcome was similar (2-y overall survival probability of 61.9% [95% confidence interval, 31.2-82.1] vs. 60.0% [95% confidence interval, 12.6-88.2], respectively, P=0.62).

[An unusual digestive complication under anti-PD-1 (pembrolizumab)]. / Une complication digestive rare sous anti-PD-1 (pembrolizumab).

The most commonly reported pattern of anti-PD-1 induced colitis is an active colitis characterized by neutrophilic inflammation and prominent apoptosis. On the other hand, reports of collagenous colitis (which is a microscopic colitis) are exceptional. In this report, we describe an unusual case of anti-PD1-associated collagenous colitis in a 76-year-old man, treated with pembrolizumab for a stage IV cutaneous melanoma. Fourteen months after the start of pembrolizumab, the patient developed a grade 3 diarrhea (up to 9 stools per day) associated with profound hypokalemia. No bacterial, viral or parasitological infectious agents were found from stool analysis. The rectosigmoidoscopy showed colonic diffuse congestion with no ulceration. Systematic biopsies were performed during endoscopy. Histologically, the fragments analyzed revealed a moderately thickened subepithelial collagen layer (20-30µm thick) associated with a mild mixed inflammatory infiltrate within the lamina propria. There were no granuloma lesions, ulcerations or viral inclusion bodies. The patient was initially successfully treated with corticosteroids (prednisone) and temporary interruption of pembrolizumab. However, during corticosteroids tapering, a relapse was observed. The treatment was switched to budesonide, leading to a complete and definitive resolution of diarrhea. To date, budesonide has been stopped and pembrolizumab has not been restarted. Currently, there is a bone progression treated by radiotherapy alone. In case of a more important progression, a systemic treatment will be secondarily discussed.

In situ multiplex immunofluorescence analysis of the inflammatory burden in kidney allograft rejection: A new tool to characterize the alloimmune response.

The exact composition of leukocyte infiltration during kidney allograft rejection is difficult to comprehend and visualize on the same biopsy slide. Using an innovative technology of multiplex immunofluorescence (mIF), we were able to detect simultaneously NK cells, macrophages, and T cells and to determine their intra- or extravascular localization using an endothelial marker. Twenty antibody-mediated rejection (ABMR), 20 T cell-mediated rejection (TCMR), and five normal biopsies were labeled, with automatic leukocyte quantification and localization. This method was compared to a classic NKp46 immunohistochemistry (IHC) with manual quantification and to mRNA quantification. mIF automatic quantification was strongly correlated to IHC (r = .91, P < .001) and to mRNA expression levels (r > .46, P < .021). T cells and macrophages were the 2 predominant populations involved in rejection (48.0 ± 4.4% and 49.3 ± 4.4%, respectively, in ABMR; 51.8 ± 6.0% and 45.3 ± 5.8% in TCMR). NK cells constituted a rare population in both ABMR (2.7 ± 0.7%) and TCMR (2.9 ± 0.6%). The intravascular compartment was mainly composed of T cells, including during ABMR, in peritubular and glomerular capillaries. However, NK cell and macrophage densities were significantly higher during ABMR in glomerular and peritubular capillaries. To conclude, this study demonstrates the feasibility and utility of mIF imaging to study and better understand the kidney allograft rejection process.

In situ multiplex immunofluorescence analysis of the inflammatory burden in kidney allograft rejection: A new tool to characterize the alloimmune response. / Immunofluorescence multiparamétrique in situ : vers l'amélioration du phénotype de l'infiltrat cellulaire au cours du rejet d'allogreffe rénale.

Background: The exact composition and localization of the inflammatory burden during allograft rejection is difficult to analyse on the same biopsy slide. We tested the feasibility of detecting four distinct markers in a same paraffin-embedded tissue section from human kidney allograft rejection by using an innovative process of multiplex immunofluorescence. Methods: Kidney allograft biopsies from 20 antibody-mediated rejection, 20 T cell-mediated rejection and five non rejection were labelled against NKp46, CD163, CD3, and CD34 respectively for NK cells, macrophages, T cells and endothelial cells. Images were scanned and cells were automatically quantified and their extra- or intravascular location determined. Conventional immunohistochemistry against NKp46 with manual quantification and real time quantitative polymerase chain reaction for evaluation of the relative messenger ribonucleic acid (mRNA) expression levels of NK, T cell and macrophage transcripts were simultaneously performed. Results: Multiplex immunofluorescence cell quantification was strongly correlated to manual quantification by immunohistochemistry (r = 0.91, P < 0.001) and to mRNA expression levels (r > 0.46, P < 0.021). T cells and macrophages were the two predominant populations involved in rejection (48.0 ± 4.4% and 49.3 ± 4.4% in antibody-mediated rejection; 51.8 ± 6.0% and 45.3 ± 5.8% in T cell-mediated rejection respectively) despite an important heterogeneity in the composition of the inflammatory burden. NK cells constituted a rare population for both T cell-mediated rejection (2.9 ± 0.6%) and antibody-mediated rejection (2.7 ± 0.7%). The intravascular compartment was mainly composed of T cells, including during antibody-mediated rejection. However, NK cells and macrophages densities were significantly higher in capillaries during antibody-mediated rejection. Conclusion: Multiplex immunofluorescence staining is a reliable technology allowing studying the exact composition and localization of the inflammatory burden during kidney allograft rejection..

[Large scale teaching in pathology]. / Pédagogie à grande échelle en ACP.

Medical education is currently facing great changes that affect all medical specialties, including anatomical pathology. Due to rapidly increasing medical knowledge and diagnostic complexity, we are living an era of teaching resources mutualization. We present different tools that allow large numbers of students to access courses, self-evaluations, and competencies assessments. MOOC platforms and e-learning platforms are central to these new online tools, which include the French National Platform of Medical Specialties, dedicated to the teaching of 50,000 medical residents in France. We also discuss "serious games" and the use of images and virtual slides in anatomical pathology teaching. These new modalities can deliver essential knowledge to large student populations, but they must be used in conjunction with adapted teacher-led courses focusing on competencies and professional skills in order to be fully effective.

Solid pseudopapillary neoplasms of the pancreas do not express major pancreatic markers in pediatric patients.

Solid pseudopapillary neoplasms (SPNs) of the pancreas are classified as "exocrine" pancreatic tumors by the World Health Organization. However, despite numerous studies using immunohistochemistry, electron microscopy, animal models, and molecular biology, the histogenesis of SPN remains unclear. At the same time, our knowledge of human pancreas development has significantly increased. It is now well known that the undifferentiated PDX1+ pancreatic progenitors proliferate and differentiate into endocrine, ductal, and acinar cells, thanks to the expression of numerous transcription factors, which can be used to better characterize pancreatic tumors. In a series of 14 pediatric SPN, we investigated the expression of 4 transcription factors associated with pancreatic development (PDX1, SOX9, PTF1A, and NKX2.2) to obtain new insights into the pathogenesis of SPN. In addition, we tested the expression of different markers of epithelial, endocrine, exocrine, and neural differentiation using both immunohistochemical and immunofluorescence analyses. All tumors displayed the typical histologic features of SPN, with both pseudopapillary and solid patterns. The immunoprofile was characterized by immunoreactivity for ß-catenin (100%), progesterone receptor (100%), cyclin D1 (100%), synaptophysin (65%), and S100 (15%). In all cases, tumor cells were negative for the following markers: PDX1, SOX9, PTF1A, NKX2.2, chromogranin A, glucagon, insulin, somatostatin, ghrelin, pancreatic polypeptide, amylase, GFAP, calretinin, EPCAM, and estrogen receptor α. To conclude, SPNs do not express major transcription factors involved in pancreatic development and differentiation, which does not allow for precise pancreatic lineage of tumor cells. Thus, additional studies are still required to determine the origin of SPN.

[Results of the Massive Open Online Course (MOOC) on cancer diagnosis and evaluation of its impact on the perception of the pathology specialty]. / Massive open online course (MOOC) sur le diagnostic des cancers : bilan et évaluation de l'impact sur la perception de l'anatomie et cytologie pathologiques.

The Massive Open Online Course (or MOOC) "Diagnostic Strategies Cancers", was hosted in autumn 2016 on the platform "France Université Numérique" and had two levels of learners: students in the field of health and biology and the general public. Of the 5285 learners in 81 different countries, 1237 (23%) were successfully certified. This MOOC was also integrated into the teaching program of medical students of Paris Diderot University and Paris 13 University. Using anonymous questionnaires before and after MOOC, it has been shown that pathology is less known than other medical specialties. Participation in this MOOC led to a marked improvement in participants' knowledge of the place and role of the pathologist in the diagnosis of cancers. Regarding the students who have followed the MOOC as part of their university course, their comments were very positive, but it is necessary to make substantial adjustments in the amounts and contents of the campus-based courses.