BACKGROUND & AIMS:Sympathetic nervous system over-activity is associated with liver disease progression and development of portal hypertension, influencing systemic inflammation. This study examined the role of the sympathetic alpha-2A adrenergic receptor (ADRA2a) and its antagonism in hepatic stellate cell (HSC) activation, a key event in fibrosis progression, in experimental metabolic dysfunction-associated steatohepatitis (MASH) and in portal pressure elevation in a cirrhotic-rat model. METHODS:An established bile duct ligation (BDL)-induced cirrhosis model (n = 14) was used to assess ADRA2a's role in portal hypertension through acute treatment with two ADRA2A antagonists (BRL44408 and yohimbine). Human (h)HSCs were incubated with either an ADRA2a agonist (guanfacine) or antagonist (BRL44408), to determine whether ADRA2a modulation altered HSC activation. We also investigated ADRA2a expression in patients with MASH fibrosis (n = 15) and conducted a longer-term yohimbine treatment study in a diet-induced MASH rodent model (n = 24). RESULTS:BRL44408 reduced portal pressure in BDL rats (12 ± 3 vs. 18 ± 4 mmHg; p <0.0001) while preserving mean arterial pressure (102 ± 16 vs. 93 ± 13 mmHg, p = 0.13). This was associated with (i) restored eNOS phosphorylation towards control levels and reduced caveolin-1 expression (p <0.05), and (ii) reduced hepatic inflammation and Kuppfer cell activation (p <0.001). Moreover, guanfacine stimulation of hHSCs increased their contractility, which was attenuated by BRL44408 (p <0.001). ADRA2A mRNA expression was increased in both patients with MASH fibrosis, and MASH rats. In MASH rats, yohimbine treatment reduced fibrosis, as measured by collagen proportional area (p <0.01). CONCLUSIONS:ADRA2A expression is increased in two experimental models of liver disease and in patients with MASH fibrosis, and it appears to contribute to the pathogenesis of portal hypertension and fibrogenesis. These findings suggest that ADRA2A antagonism may represent a potential therapeutic strategy for treating portal hypertension and fibrosis progression. IMPACT AND IMPLICATIONS:Managing fibrosis progression and portal hypertension remains a major challenge in liver disease, with fewer than 60% of patients responding to current non-selective beta-blocker therapy, despite clear evidence of increased sympathetic activation as liver disease advances. We show that the alpha-2A adrenergic receptor (ADRA2A) may represent an important pathway in hepatic stellate cell activation and may also influence additional mechanisms that regulate elevated portal pressure. These findings provide an alternative approach to beta-blockade for portal hypertension, which is limited by reductions in cardiac output and liver blood flow that can be problematic in patients with advanced disease. Data from two different rodent models support consideration of a translational clinical study of ADRA2A antagonism in portal hypertension and further investigation into the mechanisms by which ADRA2A antagonism affects metabolic dysfunction-associated steatotic liver disease.

Epstein-Barr virus (EBV) transmission from donor to naïve recipients (D+/R-) is a major risk for post-transplant lymphoproliferative disorder (PTLD). Blood EBV-DNA monitoring (EBV-DNAemia) is recommended, but the optimal blood matrix remains unclear. This 2-year prospective study of de novo kidney transplant recipients investigated the incidence and clinical significance of EBV-DNAemia in plasma and whole blood. The study estimated the positive and negative predictive values (PPV, NPV) of EBV-DNAemia kinetics for EBV-associated PTLD. Persistent EBV-DNAemia was examined as a predictor of excessive immunosuppression, defined by a composite endpoint of ≥2 infections requiring hospitalization, infection-related death, or EBV-associated PTLD. Of 509 enrolled recipients, 11 developed PTLD; 8 were EBV associated (20% of EBV D+/R- recipients, incidence rate = 8.0 (95% CI, 4.0-16.1) per 1000 patient-years). Plasma or whole-blood EBV-DNAemia were detected in 107 (21.0%) and 311 (61.1%) recipients, respectively, yielding an NPV >99% for EBV-associated PTLD in both matrices. PPVs were highest for a ≥3-fold increase in plasma EBV-DNA (PPV = 88.9%) and whole-blood EBV-DNA levels ≥50 000 IU/mL (PPV = 50.0%) among EBV D+/R- recipients. Persistent plasma EBV-DNAemia was associated with the composite endpoint (HR = 3.2; 95% CI, 1.8-5.7), predominantly driven by PTLD. Recognition of specific EBV-DNA kinetics in plasma and whole blood should promote clinical evaluation for PTLD.

Accurate stratification of Hodgkin lymphoma (HL) by immunologic/histological subtypes and Epstein-Barr virus (EBV) status is essential for epidemiological and translational research, yet large-scale testing is impractical and expensive. Digital pathology models that utilize routinely used hematoxylin and eosin (H&E) whole-slide images (WSIs) could close this gap. We developed and validated a hierarchical Vision Transformer pipeline that aggregates cell-, patch-, and region-level context to predict EBV status and the three most prevalent immunological/histological HL subtypes: nodular sclerosis (NS), mixed cellularity (MC), and nodular lymphocyte-predominant HL (NLPHL)—from H&E-stained WSIs, and additionally evaluated a standard attention-based multiple-instance learning (ABMIL) baseline for direct architectural comparison. The development pool comprised 1643 HL cases (1952 WSIs) from 18 Danish hospitals and was used for hospital-preserving 5-fold cross-validation; external validation was performed on an independent hold-out cohort of 458 cases (532 WSIs) from five hold-out hospitals. For subtype prediction, analyses were restricted to the 1560 cases belonging to NS, MC, or NLPHL. On the external EBV cohort (N=458) the hierarchical pipeline achieved an area under the receiver operating characteristic curve (ROC–AUC) of 0.73 (95% confidence interval (CI) 0.68–0.77), precision–recall (PR)–AUC 0.57 (95% CI 0.49–0.66) with recall (sensitivity) 0.74 (95% CI 0.67–0.80) and macro-F1 score 0.60 (95% CI 0.54, 0.65). For 3-class subtype prediction on 359 external cases, discrimination reached ROC–AUC 0.84 (95% CI 0.80–0.88) and PR–AUC 0.63 (95% CI 0.56–0.71) with a macro-F1 of 0.56 (95% CI 0.48, 0.64) and macro-recall 0.55 (95% CI 0.47, 0.63); residual errors were dominated by NS-MC confusions. An ABMIL baseline using the same patch embeddings achieved ROC–AUC 0.76 (95% CI 0.72–0.81) for EBV and 0.89 (95% CI 0.86–0.92) subtype prediction, outperforming the hierarchical model on both tasks. This multicenter study shows that both hierarchical and attention-based architectures can determine EBV status and major HL subtypes directly from routine H&E slides with externally validated performance across hospitals, whereas the finding that the simpler baseline outperformed the hierarchical model suggests that strong foundation-model embeddings combined with attention-based pooling may reduce the need for explicit multi-scale modelling in cohorts of this size.

Sinonasal neuroendocrine carcinomas (SN-NECs) are rare malignancies, typically affecting older individuals. This case report presents a highly malignant large-cell neuroendocrine carcinoma (NEC) originating from the nasal septum in a previously healthy young adult male. The patient initially presented with symptoms mimicking acute rhinosinusitis, such as nasal obstruction, rhinorrhoea and frontal headache, which were followed by recurrent epistaxis and double vision. Imaging revealed an extensive sinonasal (SN) tumour with local invasion and significant mass effect. Histopathology confirmed a large-cell NEC with a Ki-67 proliferation index of 80%. Urgent surgical resection was performed, followed by cisplatin and etoposide chemotherapy and radiotherapy, leading to a positive response despite complications such as thrombosis and tinnitus. This case highlights the importance of recognising red-flag symptoms, such as double vision, nasal stenosis with recurrent epistaxis and cranial nerve involvement, in SN disease to ensure early diagnosis and timely intervention.

Classic Hodgkin lymphoma (CHL) is a highly curable disease, even in advanced stages. Controversy remains over whether bone involvement negatively affects overall and progression-free survival in patients treated with intensive chemotherapy regimens. Whether cases that present with bone lesions harbor specific tumor microenvironmental features is unknown. We investigated protein expression in diagnostic lymph node biopsies from CHL patients with and without skeletal involvement at diagnosis to identify potential markers of skeletal disease. Protein expression patterns in diagnostic formalin-fixed paraffin-embedded lymphoma lymph node samples from CHL patients were analyzed by nano-liquid chromatography-tandem mass spectrometry. Patients were grouped according to skeletal involvement, which was defined as the presence of one or more FDG-avid lesions on a diagnostic FDG-PET/CT scan. Protein profiles identified patients with skeletal disease at diagnosis and showed disrupted cellular pathways, including immune system processes, cell adhesion, and cell growth/survival. Immunohistochemical evaluation also demonstrated differential expressions of angiotensin-converting enzyme (ACE), intercellular adhesion molecule 3 (ICAM3), integrin alpha-X (ITGAX), and calreticulin (CALR). In conclusion, proteomics identified altered protein expression profiles in lymph nodes among CHL cases presenting with disease disseminated to the skeletal system, which implies altered disease pathogenesis for these patients. Created with image

Posttransplant lymphoproliferative disorder (PTLD) poses a serious challenge in kidney transplant recipients. Epstein-Barr virus (EBV)-seronegative recipients have a significantly increased risk of PTLD, but few studies have investigated risk factors for PTLD in EBV-seronegative recipients in the current era of immunosuppression. This cohort study from Norway and western Denmark included first-time kidney transplant recipients between 2007 and 2021 and estimated the cumulative incidence, risk, and prognosis of PTLD. In total, 80 of 5084 recipients developed biopsy-proven PTLD (median follow-up of 6.8 years). Two-year cumulative incidence of PTLD was 7.3% in EBV-seronegative adults and 14.1% in EBV-seronegative children. The age-adjusted hazard ratio (HR) for PTLD was 30.7 (95% CI, 13.9-67.9) in EBV-seronegative vs EBV-seropositive adults and 5.4 (95% CI, 1.1-26.9) in children. Recipients receiving induction therapy with antithymocyte globulin had an increased risk of PTLD (HR, 4.4; 95% CI, 1.8-10.6), while rituximab induction was associated with a lower risk of PTLD (HR, 0.20; 95% CI, 0.03-1.49). The age-adjusted mortality rate was higher in EBV-seronegative recipients with vs without PTLD (HR, 3.3; 95% CI, 1.3-8.3). In conclusion, the risk of PTLD in EBV-seronegative kidney transplant recipients is high in the contemporary era of immunosuppression. Induction therapy should be carefully considered in this high-risk population.

Current epidemiological thinking is that classic Hodgkin lymphoma (cHL) comprises multiple aetiologically distinct disease entities that may in part be defined by either histological subtype or the presence of Epstein-Barr virus (EBV) in the malignant cells, or by both. This study aimed to advance our understanding of epidemiological differences between cHL subtypes, in particular EBV-positive and EBV-negative cHL. We retrospectively collected and EBV-typed 1992 cHL primary tumour tissues from among all 2811 patients diagnosed with incident HL in Denmark in the period 1990 through 2010 'Hodgkin lymphoma in Denmark' [HOLYDAN] project. Based on characteristics of retrieved samples combined with additional information from national registers, we projected nationwide age-, sex-, histology- and EBV-specific cHL incidence rates. The analyses demonstrated age- and sex-dependent variation in histology- and EBV-tumour status-specific cHL incidence rates, details of which yielded new aetiological clues. cHL incidence increased markedly around the age of puberty, irrespective of histological subtype and EBV status. The incidence of all subtypes of cHL increased with age after age 50 years, with the exception of EBV-negative nodular sclerosis cHL in females, which therefore showed a single peak in incidence and was higher than in males among young adults. These results were obtained in a small homogeneous population and might, therefore, only apply to rich, industrialised, Western populations. Nevertheless, we propose that puberty creates an immunological host environment conducive to cHL development irrespective of EBV status and histology, and that age-related decline in immune function facilitates the development of both EBV-positive and EBV-negative cHL.

Background: Breast cancer is the most commonly diagnosed malignancy among women worldwide. Despite high survival rates, 20%-40% of women will experience a recurrence, with risks extending beyond 20 years after diagnosis. Premenopausal women diagnosed with estrogen receptor (ER) positive disease are prescribed 5-10 years of tamoxifen therapy to prevent a recurrence. 17β-hydroxysteroid dehydrogenase 1 and 2 expression (HSD17B1 and HSD17B2, respectively) regulate the relative concentrations of estrogen metabolites and may modify tamoxifen effectiveness. We evaluated the prognostic and predictive value of these biomarkers. Methods: Premenopausal women diagnosed during 2002-2011 with a first primary stage I-III breast cancer were identified in the Danish Breast Cancer Group database, and categorized based on ER status and receipt of tamoxifen (4600 ER+/TAM+ and 1359 ER−/TAM−). HSD17B1 and HSD17B2 were assayed by immunohistochemistry and scored using automated image analysis [Visiopharm (Hoersholm, Denmark)]. The biomarkers were assessed within ER/TAM strata, to differentiate the enzymes predictive of treatment response from enzymes prognostic for breast cancer recurrence. We used Cox proportional hazards regression and probabilistic bias analysis to account for mismeasurement of biomarker expression and baseline selection bias from tumor sample availability to calculate the hazard ratios (HRs) and 95% simulation intervals (SIs) associating each biomarker with recurrence. Results: 24% of ER+/TAM+ and 13% of ER−/TAM− breast cancers had any HSD17B1 expression. In the bias-adjusted analyses, women diagnosed with tumors positive for HSD17B1 expression had an increased rate of recurrence: HR=1.40 (95% SI: 1.02, 2.92) in the ER+/TAM+ stratum, and HR=1.32 (95% SI: 0.82, 2.74) in the ER−/TAM− stratum. A 10-unit increase in HSD17B2 expression corresponded with a decreased recurrence rate among women in the ER+/TAM+ (HR=0.85, 95% SI: 0.69, 1.05) stratum, but not among women in the ER−/TAM− stratum (HR=1.07, 95% SI: 0.82, 1.42). Conclusions: We observed that HSD17B1 expression was associated with a higher rate of recurrence among premenopausal women, and that HSD17B2 expression was associated with a lower rate of recurrence among premenopausal tamoxifen-treated women diagnosed with ER+ disease. HSD17B1 may be an important prognostic marker of breast cancer recurrence among premenopausal breast cancer patients and HSD17B2 may be predictive of response among tamoxifen-treated premenopausal women diagnosed with ER+ breast cancer. Citation Format: Lindsay Jane Collin, Anders Kjaersgaard, Thomas P. Ahern, Michael Goodman, Lauren E. McCullough, Lance A. Waller, Kristina B. Christensen, Per Damkier, Stephen J. Hamilton-Dutoit, Kristina Lauridsen, Peer M. Chistiansen, Bent Ejlertsen, Henrik Toft Sorensen, Deirdre Cronin-Fenton, Timothy L. Lash. 17β-hydroxysteroid dehydrogenases 1 and 2: potential markers for breast cancer recurrence and tamoxifen resistance among premenopausal women diagnosed with breast cancer in Denmark [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 757.

INTRODUCTION:Pancreatic ductal adenocarcinoma (PDAC) has a high risk of early recurrence after surgery. We evaluated the utility of circulating tumour DNA (ctDNA) analysed at different time points as a prognostic tool. Secondary aims were prognostic value of ctDNA combined with plasma carbohydrate antigen (CA) 19-9 and prognostic value of peritoneal tumour DNA (ptDNA). METHODS:A total of 75 patients were included. Plasma samples were obtained preoperatively, 1 month, and 7-9 months after resection. Peritoneal lavage fluid (PLF) was collected preoperatively and 7-9 months after resection. Cell-free DNA (cfDNA) from plasma and ptDNA were analysed using mutation specific digital droplet PCR assays in a tumour-informed apprach. Kaplan-Meier survival curves, univariable, and multivariable Cox proportional hazard models were used to assess overall survival (OS) and recurrence-free survival (RFS). RESULTS:Preoperatively, detectable ctDNA was an independent risk factor for OS (HR = 1.88, p = 0.047). Detectable ctDNA 7-9 months after surgery was an independent risk factor for RFS (HR = 4.48, p = 0.017). Detectable ctDNA 1 month after surgery showed decreased RFS (HR = 1.98, p = 0.055). Preoperative, 1-month, and 7-9 months postoperative positivity for ctDNA and/or CA 19-9 showed a significantly worse median OS (p = 0.024, p = 0.008, and p = 0.0003). We did not find association of ptDNA with OS or RFS, but ptDNA detection 7-9 months after surgery was associated with peritoneal RFS (p = 0.003). CONCLUSION:Our data indicate that detectable ctDNA in plasma taken before and 7-9 months after surgery holds independent prognostic value in PDAC. Combination of ctDNA with CA-19-9 may be a particularly strong prognosticator, which should be confirmed in future studies.

Tissue microarrays (TMAs) are used for high-throughput biomarker discovery and validation. Although TMAs have numerous advantages, they may not always be representative of the tissue heterogeneity present in whole tissue sections (WTS) leading to inadequate biomarker quantification. In this pilot study, we studied biomarker expression in 50 randomly selected colorectal cancers and 36 microsatellite unstable cases with or without BRAF variants. We used virtual TMAs to determine the minimum number of tissue cores needed to quantify biomarkers with the same precision as when using WTS. Paraffin sections were immunohistochemically stained for markers of T cells, B cells, cancer-associated fibroblasts, and macrophages. Digitized WTS were divided into tumor center (TC) and invasive margin regions. The minimum number of virtual TMA cores in each region was determined by Bland-Altman plots with 95% limits of agreement. Bland-Altman plots showed substantial disagreement between TMAs and WTS, being highest for 3 cores and decreasing with increasing core numbers. However, even when using 8 cores, the limits of agreement between TMA and WTS were wide, indicating a high degree of measuring uncertainty using TMAs. When using 3 or 4 cores, TMAs underestimated the expression of all the biomarkers in the TC; similarly, levels of macrophage markers in the TC, and levels of B cells in both the TC and the invasive margin remained considerably underestimated, even when using the maximum number of cores possible. However, 3 cores were sufficient to adequately classify biomarkers into categoric low and high expression groups. Microsatellite unstable tumors were characterized by high heterogeneity, which was further increased in the presence of BRAF variant(s). The virtual TMA technique is a useful method to establish the minimum number of cores to be included when constructing tumor TMAs for biomarker analysis. Our results emphasize the importance of TMA validation for a specific biomarker prior to conducting larger clinical studies. (c) 2025 United States & Canadian Academy of Pathology. Published by Elsevier Inc. All rights are reserved, including those for text and data mining, AI training, and similar technologies.

PURPOSE:Premenopausal, estrogen receptor (ER)-positive breast cancer patients should receive tamoxifen for at least 5 years, but many prematurely discontinue. Activation, transport, and deactivation of tamoxifen and its metabolites are controlled by proteins encoded by genes with functional variations. We examined the impact of genetic polymorphisms in the tamoxifen pathway on early treatment discontinuation. METHODS:We included premenopausal women diagnosed with ER-positive breast cancer (2002-2011) in Denmark who initiated tamoxifen. We genotyped 26 genetic variants in 15 enzymes involved in tamoxifen metabolism. Early discontinuation was defined as tamoxifen use for < 5 years. We estimated individual and combined effects of genetic variants using a Bayesian pathway approach. We report Bayes Factors (BF), wherein values > 1 indicate support of an effect of the genetic pathway on discontinuation (compared with no effect). RESULTS:Among 3,729 patients, 536 (14%) discontinued tamoxifen within 5 years. Genetic variants involved in tamoxifen activation impacted early discontinuation (BF = 7.5), in a manner driven almost entirely by CYP2D6 activity (BF = 22.6). Several variants in CYP2D6 and transporter genes synergistically increased the hazard of early discontinuation (e.g., CYP2D6*2 and ABCC2; BF = 138). CONCLUSIONS:Variants in enzymes responsible for activating tamoxifen metabolites-particularly within CYP2D6-influence early tamoxifen discontinuation. CYP2D6 variants synergistically interact with transporter gene variants, namely ABCC2, to further raise the risk of discontinuation.

PURPOSE:Tamoxifen is guideline treatment for premenopausal women with estrogen receptor-positive (ER+) breast cancer. Therapeutic efficacy relies partly on tamoxifen biotransformation by CYP2D6, CYP2C19, and CYP3A4 enzymes. We conducted a cohort study to evaluate whether concomitant prescription of drugs that inhibit these enzymes impacted breast cancer recurrence. METHODS:We enrolled 4493 premenopausal women with stage I-III ER+ breast cancer (2002-2011) treated with tamoxifen. We defined time-varying CYP-inhibiting drug exposures as the proportion of overlapping days during the tamoxifen treatment period. We estimated associations of concomitant medication use with recurrence using: (1) Bayesian joint modeling (hazard ratio [HR] and 95% credible intervals [95% CrI]), (2) traditional Cox regression (HR and 95% confidence intervals [95% CI]). RESULTS:During tamoxifen therapy, 13% of the cohort used strong CYP2D6 inhibitors, 31% weak CYP2D6 inhibitors, 37% CYP2C19 inhibitors, and 12% CYP3A4/5 inhibitors. Bayesian joint models showed that women with ≥ 50% overlap between tamoxifen and CYP2D6 inhibitors had increased recurrence risk compared with 0% overlap (HR: 1.24, 95% CrI: 0.96, 1.58). No recurrence association was seen for CYP2C19 inhibitors (≥ 50% vs. 0%, HR = 1.0, 95% CrI: 0.69, 1.40), but traditional Cox models yielded positive associations for CYP2C19 overlap (≥ 50% vs. 0%, HR = 1.45, 95% CI: 1.07, 1.96). With Bayesian joint models, we observed no association between ≥ 50% versus 0% overlap with CYP3A4/5 inhibitors (HR: 0.84, 95% CrI: 0.32, 1.93). CONCLUSIONS:With Bayesian joint modeling, we saw a slight increase in recurrence among CYP2D6-inhibitor users, but no increase among CYP2C19- or CYP3A4-inhibitor users. Results from Cox regression models were less plausible.

Advances in treating classic Hodgkin lymphoma (cHL) have improved cure rates, with overall survival exceeding 80%, resulting in a growing population of survivors at risk of long-term complications, particularly cardiac and pulmonary toxicity. Bleomycin, a key component of combination chemotherapy, is associated with bleomycin-induced pulmonary toxicity (BPT). Using label-free quantification nano liquid chromatography-tandem mass spectrometry, protein expression in diagnostic lymphoma samples from patients with and without BPT was compared. Results showed differential protein expression and disrupted cellular pathways, suggesting biological differences in BPT risk. Immunohistochemical analysis revealed higher expression of JAK3, BID, and MMP9, and lower expression of CD20, TPD52, and PIK3R4 in patients with BPT. High BID and low CD20 expression were associated with inferior overall survival, while high BID and low JAK3 and CD20 expression were linked to poorer progression-free survival. These findings highlight altered protein profiles in pretreatment cHL biopsies associated with BPT development.

Background: The prognostic role of resection margin status following total (TP) and distal (DP) pancreatectomy for pancreatic ductal adenocarcinoma (PDAC) is insufficiently evaluated. In Denmark, pancreatic surgery, including the postoperative pathological examination of the resection specimens, is confined to four centres, all reporting to the Danish Pancreatic Cancer Database (DPCD). In this Danish population-based nationwide study on TP and DP for PDAC from 2015-2019, based on data from DPCD, we evaluated whether there is a prognostically relevant minimum margin clearance definition and whether certain margins hold independent prognostic information. Methods: Clinical and pathological data were retrieved from DPCD and supplemented by review of pathology reports and re-microscopy, if needed. One of the study pathologists performed all re-microscopy. The prognostic significance of margin status was evaluated by dichotomisation of the TP cohort (n = 101) and the DP cohort (n = 90) into involved and uninvolved groups, using different clearance definitions (0.5 - >= 3.0 mm). Results: Following TP, direct involvement of the superior mesenteric artery (SMA) margin had independent prognostic value. When using a clearance definition of >= 0.5 or >= 1.5 mm for SMA, median survival for R0 versus R1 was 19 (95% CI 14-26) versus 10 (95% CI 5-20) months (p = 0.010), and 21 (95% CI 15-30) versus 10 (95% CI 8-19) months (p = 0.011), respectively. Overall margin status was not of significant prognostic importance following neither DP nor TP. Conclusion: In this Danish population-based nationwide study, SMA margin involvement was a significant isolated prognostic factor following TP, whereas combined assessment of all circumferential margins did not hold statistically significant prognostic information. Following DP, resection margin status did not affect survival.

Background: Follicular lymphoma (FL) presents significant clinical heterogeneity, with some patients experiencing transformation into an aggressive disease, a key contributor to FL-related mortality. Based on gene expression profiles, this study aimed to provide insights into immunological differences associated with transformation. Methods: Gene expression analysis using the NanoString nCounter Tumor Signaling 360 Panel was performed on diagnostic lymphoma samples from 70 FL patients diagnosed in the rituximab era, either non-transforming FL (nt-FL, n = 34) or subsequently transforming FL (st-FL, n = 36), with paired high-grade transformed FL (tFL, n = 36) samples available. In silico immunophenotyping was performed to infer immune cell infiltration using the CIBERSORTx algorithm. Results: The gene expression analysis revealed 164 significantly differentially expressed genes, distinguishing st-FL from nt-FL and generally presenting an upregulation of B cell-related genes (CD40, IRF4, RELB), immunosuppressive molecules (IL10, SOCS3), and immune checkpoint molecules (CD276, TIM3). Analysis of immune cell proportions indicated significant differences in infiltrates of M1-like macrophages (p = 0.007) and neutrophils (p = 0.012) in nt-FL versus st-FL samples. Transformation-free survival (TFS) was associated with high numbers of both these cellular subsets (p = 0.006 and 0 = 0.002, respectively). This was even more evident when combined with inferior TFS in lymphomas with high infiltrates of both cell types (p < 0.001). After transformation, tFL samples showed a reduction in T follicular helper cells (p = 0.008) and an increase in immunosuppressive M2-like macrophages and neutrophils (p < 0.001 and p = 0.028, respectively). Conclusion: By elucidating the distinct molecular and immune landscapes of FL at the time of diagnosis and transformation, this study underscores the importance of immune microenvironment in FL transformation and patient outcome.