Artificial intelligence in digital pathology of cutaneous lymphomas: A review of the current state and future perspectives.

Primary cutaneous lymphomas (CLs) represent a heterogeneous group of T-cell lymphomas and B-cell lymphomas that present in the skin without evidence of extracutaneous involvement at time of diagnosis. CLs are largely distinct from their systemic counterparts in clinical presentation, histopathology, and biological behavior and, therefore, require different therapeutic management. Additional diagnostic burden is added by the fact that several benign inflammatory dermatoses mimic CL subtypes, requiring clinicopathological correlation for definitive diagnosis. Due to the heterogeneity and rarity of CL, adjunct diagnostic tools are welcomed, especially by pathologists without expertise in this field or with limited access to a centralized specialist panel. The transition into digital pathology workflows enables artificial intelligence (AI)-based analysis of patients' whole-slide pathology images (WSIs). AI can be used to automate manual processes in histopathology but, more importantly, can be applied to complex diagnostic tasks, especially suitable for rare disease like CL. To date, AI-based applications for CL have been minimally explored in literature. However, in other skin cancers and systemic lymphomas, disciplines that are recognized here as the building blocks for CLs, several studies demonstrated promising results using AI for disease diagnosis and subclassification, cancer detection, specimen triaging, and outcome prediction. Additionally, AI allows discovery of novel biomarkers or may help to quantify established biomarkers. This review summarizes and blends applications of AI in pathology of skin cancer and lymphoma and proposes how these findings can be applied to diagnostics of CL.

Association of endothelial to mesenchymal transition and cellular senescence with fibrosis in skin biopsies of systemic sclerosis patients: a cross-sectional study.

OBJECTIVES: Fibrosis is the dominant hallmark of systemic sclerosis (SSc). Several mechanisms have been proposed to drive the disease process, but how these relate to skin fibrosis is poorly understood. METHODS: We performed a cross-sectional study on archival skin biopsies from 18 SSc patients and four controls. Dermal fibrosis and inflammatory cell infiltration were scored in HE and Masson's Trichrome-stained sections. The presence of senescence was defined by P21 and/or P16 positivity in Ki-67 negative cells. Endothelial to mesenchymal transition (EndMT) was identified by co-localisation of CD31 and α-SMA in immunofluorescent double-stained sections, and by an enclosure of ERG positive endothelial cell nuclei by α-SMA stained cytoplasm in immunohistochemical double staining. RESULTS: The histological dermal fibrosis score of SSc skin biopsies was correlated with the modified Rodnan skin score (rho 0.55, p=0.042). Staining for markers of cellular senescence on fibroblasts was correlated with fibrosis score, inflammatory score, and CCN2 staining on fibroblasts. Moreover, EndMT was more abundant in skin from patients with SSc (p<0.01) but did not differ between groups with different fibrosis severity. The frequency of these EndMT features increased with the abundance of senescence markers and CCN2 on fibroblasts and dermal inflammation. CONCLUSIONS: EndMT and fibroblast senescence were more abundant in skin biopsies from SSc patients. This finding indicates that both senescence and EndMT are involved in the pathway leading to skin fibrosis and might be valuable biomarkers and/or possible targets for novel therapeutic interventions.

Towards diagnostic criteria for malignant deep penetrating melanocytic tumors using single nucleotide polymorphism array and next-generation sequencing.

Cutaneous deep penetrating melanocytic neoplasms frequently simulate melanoma and might occasionally progress to metastatic melanoma. Distinguishing deep penetrating nevi (DPN) and deep penetrating melanocytomas (DPM) from malignant deep penetrating tumors (MDPT) is difficult based on histopathology alone, and diagnostic criteria for MDPT are currently lacking. Using a molecular workup, we aimed to provide readily available diagnostic tools for classification of deep penetrating tumors. We used clinical follow-up and Single Nucleotide Polymorphism (SNP) array for tumor classification of 20 deep penetrating neoplasms to identify associations with histopathological, immunohistochemistry, and NGS findings. Ten neoplasms were classified as MDPT, four as DPM, and six as DPN. Two MDPT showed metastases. The following parameters were statistically significantly associated with MDPT: severe nuclear atypia (risk ratio [RR] 2.9, p < 0.05), absence of a nevus component (RR 10.0, p = 0.04), positive PRAME expression (RR 9.0, p = 0.02), complete loss of p16 expression (RR 3.5, p = 0.003), TERT-p and APC mutations (RR 11.0, p = 0.01 and RR 2.7, p = 0.002, respectively), and ≥1 additional pathogenic mutation (RR 9.0, p = 0.02). Ki-67 expression ≥ 5% was not significantly associated with MDPTs, although it was <5% in all DPNs. Three MDPT did not show nuclear ß-catenin expression despite having a CTNNB1 (n = 2) or an APC mutation (n = 1). Our findings suggest that complete loss of p16 and positive PRAME expression, a driver mutation in APC, ≥ 1 additional pathogenic mutation, especially in TERT-p, support an MDPT diagnosis in deep penetrating neoplasms. Besides severe nuclear atypia and possibly severe inflammation, we did not identify specific histopathological criteria for malignancy. Non-aberrant nuclear ß-catenin expression might not exclude a deep penetrating signature in MDPT.

Getting it Right the First Time: Frozen Sections for Diagnosing Necrotizing Soft Tissue Infections.

BACKGROUND: The aim of this study was to investigate which histopathologic findings are most indicative for necrotizing soft tissue infections (NSTIs) in ambivalent cases. METHODS: Patients undergoing surgical exploration for suspected NSTIs with obtainment of incisional biopsies for histopathological assessment were included from January 2013 until August 2019. The frozen sections and formalin-fixed paraffin-embedded (FFPE) samples were retrospectively re-assessed. The primary outcome was the discharge diagnosis. RESULTS: Twenty-seven (69%) biopsies of the 39 included samples were from patients with NSTIs. Microscopic bullae (p = 0.043), severe fascial inflammation (p < 0.001) and fascial necrosis (p < 0.001) were significantly more often present in the NSTI group compared to the non-NSTI group. Muscle edema (n = 5), severe muscle inflammation (n = 5), muscle necrosis (n = 8), thrombosis (n = 10) and vasculitis (n = 5) were most frequently only seen in the NSTI group. In thirteen tissues samples, there were some discrepancies between the severity of findings in the frozen section and the FFPE samples. None of these discrepancies resulted in a different diagnosis or treatment strategy. CONCLUSION: Microscopic bullae, severe fascial or muscle inflammation, fascial or muscle necrosis, muscle edema, thrombosis and vasculitis upon histopathological evaluation all indicate a high probability of a NSTI. At our institution, diagnosing NSTIs is aided by using intra-operative frozen section as part of triple diagnostics in ambivalent cases. Based on the relation between histopathologic findings and final presence of NSTI, we recommend frozen section for diagnosing NSTIs in ambivalent cases.

Social Identification with the Medical Profession in the Transition from Student to Practitioner.

Phenomenon: This study explores professional identity formation during a final year of medical school designed to ease the transition from student to practitioner. Although still part of the undergraduate curriculum, this "transitional year" gives trainees more clinical responsibilities than in earlier rotations. Trainees are no longer regarded as regular clerks but work in a unique position as "semi-physicians," performing similar tasks as a junior resident during extended rotations. Approach: We analyzed transcripts from interviews with 21 transitional-year medical trainees at University Medical Center Utrecht about workplace experiences that affect the development of professional identity. We used Social Identity Approach as a lens for analysis. This is a theoretical approach from social psychology that explores how group memberships constitute an important component of individual self-concepts in a process called 'social identification.' The transcripts were analyzed using thematic analysis, with a focus on how three dimensions of social identification with the professional group emerge in the context of a transitional year: cognitive centrality (the prominence of the group for self-definition), in-group affect (positivity of feelings associated with group membership) and in-group ties (perception of fit and ties with group members). Findings: Students were very aware of being a practitioner versus a student in the position of semi-physician and performing tasks successfully (i.e., cognitive centrality). Students experienced more continuity in patient care in transitional-year rotations than in previous clerkships and felt increased clinical responsibility. As a semi-physician they felt they could make a significant contribution to patient care. Students experienced a sense of pride and purpose when being more central to their patients' care (i.e., in-group affect). Finally, in extended rotations, the trainees became integrated into daily social routines with colleagues, and they had close contact with their supervisors who could confirm their fit with the group, giving them a sense of belonging (i.e., in-group ties). Insights: Using the three-dimension model of social identification revealed how students come to identify with the social group of practitioners in the context of a transitional year with extended rotations, increased clinical responsibilities, and being in the position of a "semi-physician." These findings shed light on the identity transition from student to practitioner within such a curricular structure.

Ethical considerations for modern molecular pathology.

Molecular pathology is becoming an increasingly important discipline in oncology as molecular tumor characteristics will increasingly determine targeted clinical cancer care. In recent years, many technological advances have taken place that contributed to the development of molecular pathology. However, attention to ethical aspects has been lagging behind as illustrated by the lack of publications or professional guidelines. Existing guidelines or publications on ethical aspects of DNA sequencing are mostly aimed at germline or tumor sequencing in clinical genetics or biomedical research settings. As a result, large differences have been demonstrated in the process of tumor sequencing analysis between laboratories. In this perspective we discuss the ethical issues to consider in molecular pathology by following the process of tumor DNA sequencing analysis from the preanalytical to postanalytical phase. For the successful and responsible use of DNA sequencing in clinical cancer care, several moral requirements must be met, for example, those related to the interpretation and returning of genetic results, informed consent, and the retrospective as well as future use of genetic data for biomedical research. Many ethical issues are new to pathology or more stringent than in current practice because DNA sequencing could yield sensitive and potentially relevant data, such as clinically significant unsolicited findings. The context of molecular pathology is unique and complex, but many issues are similar to those applicable to clinical genetics. As such, existing scholarship in this discipline may be translated to molecular pathology with some adaptations and could serve as a basis for guideline development. For responsible use and further development of clinical cancer care, we recommend that pathologists take responsibility for the adequate use of molecular analyses and be fully aware and capable of dealing with the diverse, complex, and challenging aspects of tumor DNA sequencing, including its ethical issues. Copyright © 2018 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

A 5-Year Evaluation of the Implementation of Triple Diagnostics for Early Detection of Severe Necrotizing Soft Tissue Disease: A Single-Center Cohort Study.

BACKGROUND: The standardized approach with triple diagnostics (surgical exploration with visual inspection, microbiological and histological examination) has been proposed as the golden standard for early diagnosis of severe necrotizing soft tissue disease (SNSTD, or necrotizing fasciitis) in ambivalent cases. This study's primary aim was to evaluate the protocolized approach after implementation for diagnosing (early) SNSTD and relate this to clinical outcome. METHODS: A cohort study analyzing a 5-year period was performed. All patients undergoing surgical exploration (with triple diagnostics) for suspected SNSTD since implementation were prospectively identified. Demographics, laboratory results and clinical outcomes were collected and analyzed. RESULT: Thirty-six patients underwent surgical exploration with eight (22%) negative explorations. The overall 30-day mortality rate was 25%, with an early, SNSTD-related mortality rate of 11% (n = 3). Of these, one patient (4%) underwent primary amputation, but died during surgery. No significant differences between baseline characteristics were found between patients diagnosed with SNSTD in early/indistinctive or late/obvious stage. Patient diagnosed at an early stage had a significantly shorter ICU stay (2 vs. 6 days, p = 0.031). Mortality did not differ between groups; patients who died were all ASA IV patients. CONCLUSION: Diagnosing SNSTD using the approach with triple diagnostics resulted in a low mortality rate and only a single amputation in a pre-terminal patient in the first 5 years after implementation. All deceased patients had multiple preexisting comorbidities consisting of severe systemic diseases, such as end-stage heart failure. Early detection proved to facilitate faster recovery with shorter ICU stay.

Loss of the tumor suppressor CYLD enhances Wnt/beta-catenin signaling through K63-linked ubiquitination of Dvl.

The mechanism by which Wnt receptors transduce signals to activate downstream beta-catenin-mediated target gene transcription remains incompletely understood but involves Frizzled (Fz) receptor-mediated plasma membrane recruitment and activation of the cytoplasmic effector Dishevelled (Dvl). Here, we identify the deubiquitinating enzyme CYLD, the familial cylindromatosis tumor suppressor gene, as a negative regulator of proximal events in Wnt/beta-catenin signaling. Depletion of CYLD from cultured cells markedly enhances Wnt-induced accumulation of beta-catenin and target gene activation. Moreover, we demonstrate hyperactive Wnt signaling in human cylindroma skin tumors that arise from mutations in CYLD. At the molecular level, CYLD interacts with and regulates K63-linked ubiquitination of Dvl. Enhanced ubiquitination of the polymerization-prone DIX domain in CYLD-deficient cells positively links to the signaling activity of Dvl. Together, our results argue that loss of CYLD instigates tumor growth in human cylindromatosis through a mechanism in which hyperubiquitination of polymerized Dvl drives enhancement of Wnt responses.

Polyalkylimide: A Nonstable Filler Over Time.

BACKGROUND: Polyalkylimide hydrogel is supposed to be a permanent, biocompatible implant. However, years after subcutaneous implantation clinical complications are seen. OBJECTIVE: To increase the understanding of the changes that occur over time in this subdermal implanted filler. MATERIALS AND METHODS: The extruded filler material of 34 patients was evaluated by histologic examination. RESULTS: In most patients who had cosmetic disturbances but no complaints, histology showed no immune cells in or around the filler material. In patients with an acute inflammatory response, giant cell invasion was seen in and around the filler material. Patients with chronic complaints showed a neutrophilic cell influx in the extruded filler. In all patients, degeneration and calcification of the material was noted. The polyalkylimide hydrogel changed over time, both macroscopically and microscopically. As in most of the patients no immune response was seen around the filler material, this may indicate that the material is biocompatible. CONCLUSION: The authors conclude that a dermal filler should not be judged solely on its biocompatible characteristics but also on the degradation process over time in the human body.

Training medical students for the twenty-first century: Rationale and development of the Utrecht curriculum "CRU+".

AIM: The aim of this report, written for the 40th anniversary issue of Medical Teacher, is to document 20 years of development of the Utrecht undergraduate medical curriculum, as both to exhibit accountability and to inform the community of the process and choices that can be made in long-term curriculum development. METHODS: We used the SPICES model, created by Medical Teacher's Editor Ronald Harden and colleagues in 1984. RESULTS: The Utrecht six-year program, now called "CRU+", has many distinct features that were introduced, most of which are well documented. A limited selection includes • A new 3+3 years Bachelor-Master structure following the EU Bologna rules leading to MD registration for cohorts of about 300. • Horizontally integrated classroom teaching of basic sciences with clinical disciplines predominantly in groups of 12 and limited lectures. • Mandatory knowledge retention tests, retesting the clinically relevant core knowledge from block tests of semesters one through four. • Vertical integration not only linking clinical experience with background knowledge, but also exemplified by a stepwise increase in health care responsibilities throughout the curriculum. • A final year focussing on growth towards the level of a primary responsible physician in a 12-week sub-internship for a limited number of patients and beds, in a chosen specialty. The student is called a semi-physician in the clerkship of this transitional year to residency. • Teaching skills training for all medical graduates, an elective teaching rotation and various peer-teaching arrangements throughout the curriculum. • Integrated semi-longitudinal clerkships with an assessment focus on entrustment decisions for Entrustable Professional Activities. CONCLUSION: UMC Utrecht has made a continuous attempt to both develop its medical curriculum and to study and report on its development in the literature, regarding new methods found and insights derived. UMC Utrecht will remain committed to developing training to meet twenty-first century demands of medical graduates.

The EPA-based Utrecht undergraduate clinical curriculum: Development and implementation.

AIM: As reports of the application of entrustable professional activities (EPAs) increase, not only for postgraduate but also for undergraduate medical education, there is a need for descriptions of what a UME curriculum with EPAs could look like. We provide such a description based on the experiences at University Medical Center Utrecht, the Netherlands, which can be used as an example by other curriculum developers. METHODS: In a three-year process, the UMC Utrecht Curriculum Committee developed a clinical workplace curriculum with an EPA structure, taking into account examples, such as the US Core EPAs for Entering Residency, and recommendations to integrate and increase the length of clerkships. RESULTS: In the resulting curriculum, operational from 2016, students train to be trusted with indirect supervision before graduation in five broad EPAs: the clinical consultation; general medical procedures; informing, advising and guiding patients and families; communicating and collaborating with colleagues; and extraordinary patient care. Each of these integrates smaller (nested) EPAs that receive focused training attention in integrated clerkships at various moments and must be signed off for entrustment with indirect supervision to complete the clerkship. DISCUSSION: The framework of EPAs went through many iterations before it was consolidated. Among the issues that required special attention was the application of a supervision levels scale for sign-off, the necessity to cover all relevant clinical content while not labeling too many small tasks each as a separate EPA, methods of EPA-focused assessment in the workplace and the creation of an e-portfolio model to serve assessment and entrustment.

Risk of Non-melanoma Skin Cancer in Patients with Atopic Dermatitis Treated with Oral Immunosuppressive Drugs.

There is uncertainty about the risk of developing non-melanoma skin cancer (NMSC), including basal cell carcinoma and squamous cell carcinoma (SCC), in patients with atopic dermatitis (AD) treated with oral immunosuppressive drugs. A total of 557 patients with AD treated with these drugs in the University Medical Center Utrecht and Groningen, the Netherlands, were analysed. NMSC after oral immunosuppressive treatment was reported in 18 patients (3.2%). The standardized incidence ratio for developing SCC was 13.1 (95% confidence interval (95% CI) 6.5-19.7). Patients developing NMSC were older at the start of therapy (p<0.001) and data lock (p<0.001) compared with patients without NMSC. No significant differences were found in sex, cumulative days of oral immunosuppressive drugs and follow-up between these groups (p=0.42, p=0.88, and p=0.34, respectively). In interpreting these results it is important to include other factors, such as lack of association between treatment duration and tumour development and the long interval between treatment discontinuation and tumour development in some patients.

The number of T cell allo-epitopes associates with CD4+ and CD8+ T-cell infiltration in pediatric cutaneous GVHD.

Risk factors for graft-versus-host disease (GVHD) following allogeneic hematopoietic stem-cell transplantation (HCST) include: HLA mismatches, sex-mismatch, and stem-cell source. We retrospectively analyzed if HLA- and sex-mismatching quantitatively affects the composition of GVHD-induced T-cell infiltrates. We quantified absolute numbers of CD4+ and CD8+ T cells present in tissue sections from skin biopsies of 23 pediatric HSCT-recipients with GVHD. HSCT with a sex-mismatched unrelated donor was associated with an increased number of CD4+ T cells when compared to a sex-matched unrelated donor (p=0.01). The absolute numbers of skin-infiltrating T cells were increased in patients expressing T-cell epitopes derived from the recipient's mismatched HLA, so called predicted indirectly recognizable HLA epitopes (PIRCHE). The combined expression of PIRCHE with a sex-mismatch resulted in the highest number of skin-infiltrating T cells. Our results indicate that an increased number of recipient-specific T-cell epitopes is associated with accumulation of CD4+ and CD8+ T cells in the skin.

Effect of the Bologna bachelor degree on considerations of medical students to interrupt or terminate their medical training.

BACKGROUND: The bachelor-master system potentially enables medical students to stop or temporary interrupt their training after obtaining a bachelor degree. A survey at the time of introduction of this two-cycle model in Dutch medical education showed little interest among students in these possibilities. AIMS: To investigate students' considerations to stop or pause now that this model is well established. METHODS: Questionnaires were sent to 314 second year and 348 third year bachelor students and 256 first year master students at University Medical Center Utrecht. RESULTS: Response rates were 33.4% for the second year and 42.0% for the third year bachelor students and 48.8% for the master students. Of all these students, one to three percent seriously considered a permanent stop. Of the bachelor students, about one quarter seriously considered a temporary stop after finishing the bachelor program. Of the master students, one in seven indicated that they did take a break at that opportunity. CONCLUSIONS: Awarding the bachelor degree does not particularly encourage students to discontinue their medical study. Our results are comparable to the results of the survey at the time of the introduction of the bachelor-master system, which supports our previous conclusion.

Microbubble-Assisted Ultrasound for Drug Delivery to the Retina in an Ex Vivo Eye Model.

Drug delivery to the retina is one of the major challenges in ophthalmology due to the biological barriers that protect it from harmful substances in the body. Despite the advancement in ocular therapeutics, there are many unmet needs for the treatment of retinal diseases. Ultrasound combined with microbubbles (USMB) was proposed as a minimally invasive method for improving delivery of drugs in the retina from the blood circulation. This study aimed to investigate the applicability of USMB for the delivery of model drugs (molecular weight varying from 600 Da to 20 kDa) in the retina of ex vivo porcine eyes. A clinical ultrasound system, in combination with microbubbles approved for clinical ultrasound imaging, was used for the treatment. Intracellular accumulation of model drugs was observed in the cells lining blood vessels in the retina and choroid of eyes treated with USMB but not in eyes that received ultrasound only. Specifically, 25.6 ± 2.9% of cells had intracellular uptake at mechanical index (MI) 0.2 and 34.5 ± 6.0% at MI 0.4. Histological examination of retinal and choroid tissues revealed that at these USMB conditions, no irreversible alterations were induced at the USMB conditions used. These results indicate that USMB can be used as a minimally invasive targeted means to induce intracellular accumulation of drugs for the treatment of retinal diseases.

Lack of concentration-dependent local toxicity of highly concentrated (5%) versus conventional 0.5% bupivacaine following musculoskeletal surgery in a rat model.

PURPOSE: Various sustained-release formulations incorporate high bupivacaine concentrations but data on local toxicity is lacking. This study explores local toxic effects of highly concentrated (5%) bupivacaine compared to clinically used concentrations in vivo following skeletal surgery, to assess the safety of sustained-release formulations with high bupivacaine concentrations. METHODS: Sixteen rats underwent surgery, in which screws with catheters affixed were implanted in the spine or femur in a factorial experimental design, allowing single-shot or continuous 72 h local administration of 0.5%, 2.5% or 5.0% bupivacaine hydrochloride. During the 30-day follow-up, animal weight was recorded and blood samples were obtained. Implantation sites underwent histopathological scoring for muscle damage, inflammation, necrosis, periosteal reaction/thickening and osteoblast activity. Effects of bupivacaine concentration, administration mode and implantation site on local toxicity scores were analyzed. RESULTS: Chi-squared tests for score frequencies revealed a concentration-dependent decrease in osteoblast count. Moreover, spinal screw implantation led to significantly more muscle fibrosis but less bone damage than femoral screw implantation, reflecting the more invasive muscle dissection and shorter drilling times related to the spinal procedure. No differences between bupivacaine administration modes regarding histological scoring or body weight changes were observed. Weight increased, while CK levels and leukocyte counts decreased significantly during follow-up, reflecting postoperative recovery. No significant differences in weight, leukocyte count and CK were found between interventional groups. CONCLUSION: This pilot study found limited concentration-dependent local tissue effects of bupivacaine solutions concentrated up to 5.0% following musculoskeletal surgery in the rat study population.

Dupilumab-Associated Lymphoid Reactions in Patients With Atopic Dermatitis.

Importance: Since the increased use of dupilumab for atopic dermatitis (AD) in daily practice, several cases have been reported on the development of cutaneous T-cell lymphomas (CTCL) and lymphoid infiltrates. Objective: To provide insight in the clinical and histopathologic features of patients with AD clinically suspected for CTCL during dupilumab treatment. Design, Setting, and Participants: This retrospective observational case series included adult (≥18 years) patients with AD treated with dupilumab between October 2017 and July 2022 at the University Medical Center Utrecht in the Netherlands. Main outcomes and measures: Relevant patient, disease, and treatment characteristics were evaluated. Skin biopsies before, during, and after treatment were collected and reassessed. Results: Fourteen patients (54.5% male) with a median (IQR) age of 56 (36-66) years suspected for CTCL with deterioration of symptoms during dupilumab treatment were included. Of 14 patients, 3 were retrospectively diagnosed with preexistent mycosis fungoides (MF). Eleven patients with AD were eventually diagnosed with a lymphoid reaction (LR). These patients showed MF-like symptoms; however, histopathologic findings were different, and included sprinkled distribution of small hyperchromatic lymphocytes in the upper epidermal section, a dysregulated CD4:CD8 ratio, and CD30 overexpression, without loss of CD2/CD3/CD5. The median time to clinical worsening was 4.0 months (IQR, 1.4-10.0). Posttreatment biopsies showed complete clearance of the LR in all patients. Conclusions and relevance: This study found that dupilumab treatment can cause a reversible and benign LR, which mimics a CTCL, though has distinctive histopathologic features.

Histological assessment of the sclerotic graft-versus-host response in the humanized RAG2-/-γc-/- mouse model.

Graft-versus-host disease (GVHD) remains a frequently occurring and difficult-to-treat complication in human allogeneic stem cell transplantation. Murine transplantation models are often used to study and understand the complex pathogenesis of GVHD and to explore new treatment strategies. Although GVHD kinetics may differ in murine and human models, adequate models are essential for identification of the crucial factors responsible for the major pathology in GVHD. We present a detailed description of the specific histological features of a graft-versus-host-induced fibrotic response in xenogeneic RAG2(-/-)γc(-/-) mice after total body irradiation and injection with human peripheral blood mononuclear cells. We describe the full morphological features of this reaction, including a detailed analysis of the specific tissue infiltration patterns of the human peripheral blood mononuclear cells. Our data show the development of fibrosis, predominantly near blood vessels, and reveal different cell populations and specific cell migration patterns in the affected organs. The combination of immunohistochemical cell characterization and mRNA expression analysis of both human (donor)- and murine (host)-derived cytokines reveals an interaction between host tissues and donor-derived cells in an entangled cytokine profile, in which both donor- and host-derived cytokines contribute to the formation of fibrosis.

No non-sentinel node involvement in melanoma patients with limited Breslow thickness and low sentinel node tumour load.

AIMS: Most melanoma patients with a positive sentinel node (SN) undergo completion lymph node dissection and frequently experience associated morbidity. However, only 10-30% of SN-positive patients have further lymph node metastases. The aim of the present study was to predict the absence of non-SN metastases in a multicentre study of patients with a positive SN based on primary melanoma features and SN tumour load. METHODS AND RESULTS: Of 70 SN positive patients, 18 had non-SN metastases. Penetrative depth of metastatic cells into the SN and SN tumour load was assessed by morphometry. None of the 14 patients (20%) with a Breslow thickness <2.0 mm and an SN tumour load <0.2 mm2 had non-SN metastases. Similarly, none of the 15 patients (21%) with a Breslow thickness <2.0 mm and SN penetrative depth <600 µm had non-SN metastases. Lastly, none of the 14 patients (20%) with a Breslow thickness <2.0 mm and a diameter of the largest SN deposit <500 µm had non-SN metastases. CONCLUSIONS: A combination of limited Breslow thickness and low SN tumour load predicts absence of non-SN metastases in melanoma patients with a positive SN with high accuracy. We propose that this subgroup may be spared completion lymph node dissection.