Ramon Robledano

Background: Follicular lymphoma (FL) and diffuse large B-cell lymphoma (DLBCL) exhibit substantial heterogeneity, reflecting the diversity of the germinal center (GC). Histologic transformation of FL to DLBCL is associated with poor prognosis, yet robust biomarkers predicting transformation remain limited. Methods: We integrated single-cell DNA sequencing, single-cell RNA sequencing, and spatial transcriptomics in diagnostic lymph-node biopsies from non-transformed FL (ntFL), transformed FL (tFL), and DLBCL to characterize clonal states and immune niches in GC lymphomas. T-cell signatures associated with transformation were evaluated in an independently published single-cell FL dataset. Results: Transcriptional profiling revealed similarities between tFL and DLBCL, consistent with a GC-related malignant program. The tFL microenvironment showed enrichment of exhausted CD4⁺ regulatory and CD8⁺ effector T cells, together with CD4⁺ follicular helper T cells (Tfh) displaying an adhesion-related phenotype. Spatial analysis suggested increased proximity of exhausted/immunosuppressive T cells and enhanced Tfh-B-cell interactions in tFL compared with ntFL. These immune signatures were also observed in an external cohort and were associated with early transformation. In addition, clonal hematopoiesis-associated mutations were detected in microenvironmental cells across samples, suggesting a potential contribution to the lymphoma microenvironment. Conclusions: This work demonstrates the feasibility of integrating single-cell and spatial analyses in GC lymphomas and provides a framework for investigating tumor heterogeneity and immune organization. These findings may inform future studies on biomarker development and the rational design of immunotherapies.

Introduction: Pathology requires the integration of macroscopic and microscopic findings for an accurate diagnosis. Fine needle aspiration biopsy (FNA) traditionally became the domain of radiologists with the introduction of ultrasound; however, its increased accessibility has allowed other specialists, including pathologists, to incorporate it into their daily practice. Both ultrasound-guided FNA and core needle biopsy (CNB) performed by interventional pathologists have proven valuable tools in the diagnosis of lymph node lesions. Materials and Methods: An observational, descriptive, retrospective study was conducted at Hospital Universitario del Henares, analysing 134 FNABs and 31 CNBs of lymph node lesions between 2023 and 2024. The diagnostic yield of both techniques and their correlation were evaluated. Results: Ultrasound facilitated better lesion characterization. FNA demonstrated a diagnostic yield of 98%, with a 94% correlation with CNB results. The Sydney system 2020 was applied to FNA reporting in lymphatic node. An equivalent classification system for CNB is proposed. Conclusion: The performance of FNA and CNB by pathologists optimizes diagnosis, reduces time and costs, and strengthens their role in minimally invasive diagnostics. Adoption of a unified classification system for CNB lesions would facilitate communication between specialists.

Lung cancer continues to be the leading cause of cancer‐related mortality, with cytologic samples often serving as the primary diagnostic tool. However, differentiating between benign and malignant processes in lung cytology can be difficult because various non‐neoplastic conditions closely resemble malignant lesions, which may lead to misdiagnosis. This review offers nine essential tips to help cytopathologists prevent false‐positive diagnoses of malignancy in non‐neoplastic processes. By examining common non‐neoplastic entities that can mimic lung malignancies, this review emphasizes their key cytomorphologic features and distinguishing characteristics. The authors stress the importance of a thorough clinical and radiologic context, slide background evaluation, and identification of cytomorphologic features for an accurate diagnosis of these mimics. The objective of this review was to enhance diagnostic accuracy and prevent misdiagnosis, thereby improving patient management in lung cancer cytopathology.

In the 21st century, there has been a dramatic shift in the diagnosis and management of non-small cell lung carcinoma (NSCLC), with an increasing use of minimally invasive tissue acquisition methods. Current treatments require morphologic subtyping and biomarker information in all cases. Determining such biomarkers is a continuously evolving field; current guidelines state that the determination of mutations on the Epidermal Growth Factor (EFGR), Kirsten Rat Sarcoma viral oncogene homolog (KRAS), Proto-oncogene B-Raf (BRAF), Human epidermal growth factor receptor 2 (HER2) and Anaplastic Lymphoma Kinase (ALK), genes as well as fusions on genes such as ROS Proto-Oncogene 1, Receptor Tyrosine Kinase (ROS1), MET proto-oncogene, receptor tyrosine kinase (MET), RET proto-oncogene (RET), and the Neurotrophic Tyrosine Receptor Kinase (NTRK) family is mandatory. While analyzing such alterations, some of them were first reported to be mutually exclusive, although in recent years, it has been shown otherwise in some of these cases. Moreover, so was the case with the concomitant expression of NTRK fusions and EGFR mutations. We present a case report of a patient with concomitant EGFR mutation and NTRK1 fusion.

Brain radiation necrosis (RN) is a subacute or late adverse event following radiotherapy, involving an exacerbated inflammatory response of the brain tissue. The risk of symptomatic RN associated with stereotactic radiosurgery (SRS) as part of the treatment of brain metastases (BMs) has been a subject of recent investigation. The activation of the signal transducer and activator of transcription 3 (STAT3) was shown in reactive astrocytes (RA) associated with BMs. Given that the pathophysiological mechanisms behind RN are not fully understood, we sought to investigate the role of STAT3 among other inflammatory markers in RN development. A mouse model of RN using clinical LINAC-based SRS was designed to induce brain necrosis with the administration of 50 Gy in a single fraction to the left hemisphere using a circular collimator of 5 mm diameter. Immunohistochemistry and multiplex staining for CD4, CD8, CD68, GFAP, and STAT3 were performed. For validation, eleven patients with BMs treated with SRS who developed symptomatic RN and required surgery were identified to perform staining for CD68, GFAP, and STAT3. In the mouse model, the RN and perinecrotic areas showed significantly higher staining for F4/80+ and GFAP+ cells, with a high infiltration of CD4 and CD8 T-lymphocytes, when compared to the non-irradiated cerebral hemisphere. A high number of GFAP+pSTAT3+ and F4/80+pSTAT3+ cells was found in the RN areas and the rest of the irradiated hemisphere. The analysis of human brain specimens showed that astrocytes and microglia were actively phosphorylating STAT3 in the areas of RN and gliosis. Phosphorylated STAT3 is highly expressed in the microglia and RA pertaining to the areas of brain RN. Targeting STAT3 via inhibition represents a promising strategy to ameliorate symptomatic RN in BM patients undergoing SRS.