Fluorescence confocal microscopy can accelerate diagnosis of cervical lymphadenopathy.

Fluorescence confocal microscopy (FCM) is an optical technique that uses laser light sources of different wavelengths to generate real-time images of fresh, unfixed tissue specimens. Unlike conventional histological evaluation methods, FCM is able to assess fresh tissue samples without the associated cryo artifacts typically observed after frozen sectioning. The purpose of this study was to evaluate the utility of FCM imaging in the differential diagnosis of cervical lymphadenopathy. Twenty-two cervical lymph node specimens from patients with lymphadenopathy of unknown origin were imaged by FCM. Two pathologists independently evaluated the scans for suspicion of malignancy and preliminary diagnosis. Malignancy was reliably excluded or confirmed by both pathologists with a sensitivity of 90.9% for pathologist 1 and 100% for pathologist 2. The specificity was 100% for both pathologists. For the preliminary diagnosis, almost perfect agreement with the final diagnosis was observed for both pathologists (κ= 0.94 for pathologist 1 and κ= 1.00 for pathologist 2). This is the first study to investigate lymph node specimens with different diagnoses, including lymphoma, using FCM. Our results indicate that differential diagnosis of lymph node specimens is feasible in FCM images, thus encouraging further exploration of FCM imaging in lymph node specimens to accelerate diagnosis and open the possibility of digitizing diagnosis on fresh, unfixed tissue.

Transient Acquired Amegakaryocytic Thrombocytopenia in the Setting of Severe Sepsis: A Case Report.

Acquired amegakaryocytic thrombocytopenia (AATP) is a rare disorder in which severely low platelet levels occur due to reduced or complete absence of megakaryocytes in the bone marrow. The pathophysiology of this disease is not fully understood, although anti-thyroid peroxidase antibodies (anti-TPO) binding to cellular-myeloproliferative leukemia (c-mpl) receptors is a proposed mechanism. Currently, no standard published guideline for treatment exists, but immunosuppressive therapies have been used based on the proposed mechanism and associated conditions. We present a case of a 57-year-old male who presented to the hospital with a 3-day history of progressive weakness and dysphagia. He had recently been discharged from an outside health system after evaluation for suspected gastrointestinal bleeding, although esophagogastroduodenoscopy and colonoscopy did not uncover a source of bleeding. Fifteen days later, he was admitted to our hospital for septic shock and acute renal failure with suspected lower gastrointestinal bleeding (melena on presentation). He was found to have a rapidly declining platelet count with a nadir of 0. Due to severe thrombocytopenia, filgrastim was administered. A bone marrow biopsy revealed findings consistent with amegakaryocytosis with otherwise preserved cell lines. Hematologic labs improved with the initiation of appropriate treatment for severe sepsis. After performing an extensive workup, the likely etiology of transient AATP in this case was severe sepsis-induced immune dysregulation and bone marrow suppression.

Updates on germline predisposition in pediatric hematologic malignancies: What is the role of flow cytometry?

Hematologic neoplasms with germline predisposition have been increasingly recognized as a distinct category of tumors over the last few years. As such, this category was added to the World Health Organization (WHO) 4th edition as well as maintained in the WHO 5th edition and International Consensus Classification (ICC) 2022 classification systems. In practice, these tumors require a high index of suspicion and confirmation by molecular testing. Flow cytometry is a cost-effective diagnostic tool that is routinely performed on peripheral blood and bone marrow samples. In this review, we sought to summarize the current body of research correlating flow cytometric immunophenotype to assess its utility in diagnosis of and clinical decision making in germline hematologic neoplasms. We also illustrate these findings using cases mostly from our own institution. We review some of the more commonly mutated genes, including CEBPA, DDX41, RUNX1, ANKRD26, GATA2, Fanconi anemia, Noonan syndrome, and Down syndrome. We highlight that flow cytometry may have a role in the diagnosis (GATA2, Down syndrome) and screening (CEBPA) of some germline predisposition syndromes, although appears to show nonspecific findings in others (DDX41, RUNX1). In many of the others, such as ANKRD26, Fanconi anemia, and Noonan syndrome, further studies are needed to better understand whether specific flow cytometric patterns are observed. Ultimately, we conclude that further studies such as large case series and organized data pipelines are needed in most germline settings to better understand the flow cytometric immunophenotype of these neoplasms.

Enhancing hematopathology peripheral blood smear education through asynchronous video material: A pilot report.

This study explores the effectiveness of asynchronous video material as a supplementary educational tool for trainees in hematopathology. Traditional pedagogical methods often rely heavily on faculty involvement, potentially limiting the breadth of information trainees receive due to constraints in faculty time and the variety of cases covered in a limited time interval/rotation. Asynchronous video-based learning presents a potential solution to these challenges. This concept has been utilized effectively in various fields of medical education. In this study, we describe our implementation of an educational program utilizing asynchronous video material to supplement traditional learning methods for peripheral blood smear interpretation for learners on a hematopathology clerkship. Following a pre-test/post-test assessment with 13 trainees, we analyzed the correlation between video viewing percentage and changes in test scores. The results indicate an improvement in test scores following exposure to video content, supporting the positive impact of asynchronous video material on hematopathology education. Trainees had positive feedback regarding this new educational tool. This study suggests that such self-directed learning could enhance traditional teaching methods, ensuring broader and more consistent coverage of hematopathology concepts.

A Rare Case of Early T-Precursor Lymphoblastic Lymphoma (ETP-LBL) in a Child With Nijmegen Breakage Syndrome.

Lymphoblastic lymphoma (LBL) with an early T-cell precursor phenotype has only been rarely reported. Nijmegen breakage syndrome (NBS) is an inherited chromosomal instability disorder with known predisposition to malignancies that is very rare as well. We report a case of early T-precursor LBL (ETP-LBL) in a patient with NBS, a rare combination that has not been reported. We raise the question of whether a chromosomal instability disorder such as NBS increases the propensity for early T-precursor acute lymphoblastic leukemia/lymphoma (ETP-ALL/LBL), given that ETP-ALL has been shown to have increased genomic instability compared to T-ALL.

Interfollicular Classic Hodgkin Lymphoma: Report of a Case and a Brief Review of Literature.

Interfollicular Hodgkin lymphoma (IHL) has been rarely reported in the literature and is recognized by the WHO Classification as a morphologic pattern sometimes seen in mixed cellularity classic Hodgkin lymphoma (CHL). The changes may be subtle due to preservation of architecture. We report a case of a 9-year-old male with IHL showing preserved follicular architecture but with the presence of interfollicular infiltrates consisting of eosinophils, plasma cells, and Hodgkin-Reed-Sternberg (HRS) cells. Immunophenotyping confirmed the morphologic suspicion for IHL. A discussion and review of the literature are offered. We conclude that IHL is a variant that requires a high index of suspicion, as it may be easily missed due to the subtle morphologic features and preserved architecture seen in most cases. We further emphasize that unexplained interfollicular infiltrates of eosinophils may be clues that should prompt a search of HRS cells and consideration of immunohistochemical staining if needed.

Comprehensive morphologic characterization of bone marrow biopsy findings in a large cohort of patients with VEXAS syndrome: A single-institution longitudinal study of 111 bone marrow samples from 52 patients.

OBJECTIVES: VEXAS syndrome is an adult-onset autoinflammatory disease caused by a somatic pathogenic mutation in the UBA1 (ubiquitin-like modifier activating enzyme 1) gene. Patients present with rheumatologic manifestations and cytopenias and may have an increased predisposition to myelodysplastic syndrome (MDS) and plasma cell neoplasms. Prior studies have reported on the peripheral blood and bone marrow findings in patients with VEXAS syndrome. Due to the protean clinical presentation and lack of specificity of morphologic features (eg, vacuoles in early erythroid and granulocytic precursors), an optimal screening methodology to identify these patients in a timely fashion is desirable. METHODS: To further evaluate and describe the salient diagnostic morphologic features in VEXAS syndrome, we carried out a comprehensive study of the largest single-institution cohort to date. Diagnostic and follow-up bone marrow biopsy specimens from 52 male patients with molecularly identified VEXAS syndrome underwent central review. RESULTS: Cytopenias were common in all cases, primarily macrocytic anemia, monocytopenia, and thrombocytopenia. Bone marrow aspirate and biopsy were often hypercellular, with an increased myeloid/erythroid ratio, granulocytic hyperplasia with left shift, erythroid left shift, and megakaryocyte hyperplasia, which exhibited a range of striking morphologic findings. Distinctly vacuolated myeloid and erythroid precursors were seen in more than 95% of cases. CONCLUSIONS: Our data reveal potential novel diagnostic features, such as a high incidence of monocytopenia and distinct patterns of atypical megakaryopoiesis, that appear different from dysmegakaryopoiesis typically associated with MDS. In our experience, those findings are suggestive of VEXAS, in the appropriate clinical context.

Validation of Artificial Intelligence (AI)-Assisted Flow Cytometry Analysis for Immunological Disorders.

Flow cytometry is a vital diagnostic tool for hematologic and immunologic disorders, but manual analysis is prone to variation and time-consuming. Over the last decade, artificial intelligence (AI) has advanced significantly. In this study, we developed and validated an AI-assisted flow cytometry workflow using 379 clinical cases from 2021, employing a 3-tube, 10-color flow panel with 21 antibodies for primary immunodeficiency diseases and related immunological disorders. The AI software (DeepFlow™, version 2.1.1) is fully automated, reducing analysis time to under 5 min per case. It interacts with hematopatholoists for manual gating adjustments when necessary. Using proprietary multidimensional density-phenotype coupling algorithm, the AI model accurately classifies and enumerates T, B, and NK cells, along with important immune cell subsets, including CD4+ helper T cells, CD8+ cytotoxic T cells, CD3+/CD4-/CD8- double-negative T cells, and class-switched or non-switched B cells. Compared to manual analysis with hematopathologist-determined lymphocyte subset percentages as the gold standard, the AI model exhibited a strong correlation (r > 0.9) across lymphocyte subsets. This study highlights the accuracy and efficiency of AI-assisted flow cytometry in diagnosing immunological disorders in a clinical setting, providing a transformative approach within a concise timeframe.

EBV-Positive Intravascular Large B-Cell Lymphoma of the Small Intestine: A Case Report and Literature Review.

Intravascular large B-cell lymphoma (IVLBCL) is a rare lymphoma that affects the brain, skin, and bone marrow. We describe the case of a 75-year-old man who was admitted to the hospital after 4 h of stomach aches. A thorough physical examination indicated stomach discomfort and skin discoloration. Laboratory tests revealed thrombocytopenia and elevated lactate dehydrogenase levels. A computed tomography scan of the abdomen revealed that the small intestine wall was thickened, edematous, and necrotic. The necrotic small bowel was surgically removed, revealing many little round, homogenous, and unusual cells in the mesenteric vein. In-situ hybridization revealed that these cells were positive for PAX5, CD20, CD79a, CD10, and BCL2, as well as Epstein-Barr virus-encoded small RNA. After 1 week of hospitalization without treatment, the patient was diagnosed with IVLBCL and died of multiple organ dysfunction syndrome. IVLBCL is a rare illness that affects the small intestine and possibly the gastrointestinal system. It has an insidious start, a fast development, and a dismal prognosis. Knowing its clinicopathologic traits helps in understanding the illness, making an early diagnosis, and preventing rapid worsening.

Pediatric Hematopathology in the Era of Advanced Molecular Diagnostics: What We Know and How We Can Apply the Updated Classifications.

Pediatric hematologic malignancies often show genetic features distinct from their adult counterparts, which reflect the differences in their pathogenesis. Advances in the molecular diagnostics including the widespread use of next-generation sequencing technology have revolutionized the diagnostic workup for hematologic disorders and led to the identification of new disease subgroups as well as prognostic information that impacts the clinical treatment. The increasing recognition of the importance of germline predisposition in various hematologic malignancies also shapes the disease models and management. Although germline predisposition variants can occur in patients with myelodysplastic syndrome/neoplasm (MDS) of all ages, the frequency is highest in the pediatric patient population. Therefore, evaluation for germline predisposition in the pediatric group can have significant clinical impact. This review discusses the recent advances in juvenile myelomonocytic leukemia, pediatric acute myeloid leukemia, B-lymphoblastic leukemia/lymphoma, and pediatric MDS. This review also includes a brief discussion of the updated classifications from the International Consensus Classification (ICC) and the 5th edition World Health Organization (WHO) classification regarding these disease entities.

Fifth Edition of the World Health Classification of Tumors of the Hematopoietic and Lymphoid Tissue: Myeloid Neoplasms.

In this manuscript, we review myeloid neoplasms in the fifth edition of the World Health Organization classification of hematolymphoid tumors (WHO-HEM5), focusing on changes from the revised fourth edition (WHO-HEM4R). Disease types and subtypes have expanded compared with WHO-HEM4R, mainly because of the expansion in genomic knowledge of these diseases. The revised classification is based on a multidisciplinary approach including input from a large body of pathologists, clinicians, and geneticists. The revised classification follows a hierarchical structure allowing usage of family (class)-level definitions where the defining diagnostic criteria are partially met or a complete investigational workup has not been possible. Overall, the WHO-HEM5 revisions to the classification of myeloid neoplasms include major updates and revisions with increased emphasis on genetic and molecular drivers of disease. The most notable changes have been applied to the sections of acute myeloid leukemia and myelodysplastic neoplasms (previously referred to as myelodysplastic syndrome) with incorporation of novel, disease-defining genetic changes. In this review we focus on highlighting the updates in the classification of myeloid neoplasms, providing a comparison with WHO-HEM4R, and offering guidance on how the new classification can be applied to the diagnosis of myeloid neoplasms in routine practice.

T-cell large granular lymphocytic leukemia in Vietnam: Using microscope-to-screen videoconferencing to improve diagnosis.

OBJECTIVES: Leukemia diagnosis in Vietnam is limited by a lack of hematopathology training and expert consultation as well as the cost of high-magnification digitization of hematology slides. Screen-sharing software allows international collaboration with experienced hematopathologists for improved diagnostic accuracy. METHODS: A hematopathology education and consultation program was proposed for Vietnam hospitals. By appointment, pathologists in Vietnam with access to a microscope camera, imaging software, and high-speed internet were invited to review slides and data with a volunteer board-certified hematopathologist in the United States using secure videoconferencing software. A single hospital in southern Vietnam assigned a pathologist proficient in English to access this service. All consultations from this site with clinicopathologic information were logged. After a 2-year period of online consultation, case slides for selected diagnoses were reviewed under the microscope in Vietnam to assess concordance. RESULTS: In total, 135 consultations were logged, 53 of which were for blood and bone marrow. T-cell large granular lymphocytic leukemia (T-LGLL) was 1 of the most frequent bone marrow consultation-related diagnoses; all diagnoses of this entity were confirmed by in-person microscopy (100% concordance). A records search and physician surveys found no prior documented diagnoses of T-LGLL made in Vietnam before this education and consultation program. CONCLUSIONS: Our virtual consultation model has improved patient care in Vietnam by providing correct diagnoses to inform best practices in treatment. As a result of our program, the first Vietnam diagnoses of T-LGLL were made and may help expand on the literature in this area. This model could provide cost-effective, real-time consultation and education services for pathologists in underserved communities.

An Unusual Case of Extranodal Marginal Zone Lymphoma Mimicking Abdominal Cocoon Syndrome in an Adolescent Patient.

Extranodal marginal zone lymphoma of mucosa-associated lymphoid tissue (MALT lymphoma) is an indolent non-Hodgkin lymphoma rarely seen in pediatric patients. MALT lymphoma most commonly involves the gastrointestinal tract or peri-orbital tissues, potentially as sequela of chronic antigenic stimulation or immune dysregulation. Rare cases of MALT lymphoma arising from the gynecologic tract have been reported in older adult patients. We present the unique case of a 16-year-old postpubescent female with MALT lymphoma localized to the gynecologic tract, who initially presented with abdominal fullness, abnormal uterine bleeding, and obstructive acute kidney injury secondary to urinary outflow obstruction. Intraoperatively, dense fibrosis of the uterus and left fallopian tube was noted which mimicked abdominal cocoon syndrome. She was treated with 6 cycles of bendamustine and rituximab with complete anatomic and metabolic remission. In this report we highlight a very unusual presentation of a rare malignancy in the pediatric population as well as unique treatment considerations given this patient's young age and tumor location.

Determination of age-dependent bone marrow normocellularity.

OBJECTIVES: Determination of bone marrow cellularity is a key part of bone marrow examination because it provides a small window into a patient's current state of hematopoietic well-being. Traditionally, bone marrow cellularity is estimated semiquantitatively through microscopic examination of core biopsy specimens harvested from the iliac crest of the pelvic bone. Bone marrow cellularity is then designated as hypercellular, normocellular, or hypocellular based on the patient's age. This assessment can have significant clinical impact, but the variation in the age-adjusted normocellularity range is not sufficiently characterized because of a lack of study data, especially in older patients (those older than 70 years of age). This study further established the normal range of bone marrow cellularity, particularly in older adults. METHODS: In this study, 570 benign staging and healthy donor bone marrows from patients 1 year to 93 years of age were analyzed for cellularity. RESULTS: Linear regression modeling demonstrates that cellularity in adults declines approximately 3% per decade, including after the seventh decade of life. The 90% reference interval for normocellularity in United States is 30% to 75% for those aged 18 to 90 years. CONCLUSIONS: The findings revealed a more stable and slower rate of decline in cellularity with age in adults than the widely used linear model of "100% minus the patient age in decades." Normocellularity is better modeled based on age group. In those younger than 20 years of age, normocellularity ranges from 45% to 85% (mean [SD], 65% [20%]), as defined by Friebert et al in 1998. Based on our study finding of a little less than 3% decline per decade of age, the following is our recommendation for normocellularity range: For individuals 20 to 40 years of age, it ranges from 40% to 70% (mean [SD], 55% [15%]); for individuals 40 to 60 years of age, it ranges from 35% to 65% (mean [SD], 50% [15%]); and for individuals older than 60 years of age, it ranges from 30% to 60% (mean [SD], 45% [15%]). Interestingly, those older than 70 years of age do not show a significant decrease from those aged 60 to 69 years.

Cutaneous Manifestations of Myeloid Neoplasms Exhibit Broad and Divergent Morphologic and Immunophenotypic Features but Share Ancestral Clonal Mutations With Bone Marrow.

In this study, we performed a comprehensive molecular analysis of paired skin and peripheral blood/bone marrow (BM) samples from 17 patients with cutaneous myeloid or cutaneous histiocytic-dendritic neoplasms. The cutaneous manifestations included 10 patients with cutaneous acute myeloid leukemia (c-AML), 2 patients with full or partial Langerhans cell differentiation, 2 patients with blastic plasmacytoid dendritic cell neoplasms (BPDCN), 1 patient with both Langerhans cell differentiation and BPDCN, and 2 patients with full or partial indeterminate dendritic cell differentiation. Seven of the 10 c-AML patients (70%) exhibited concurrent or subsequent marrow involvement by acute myeloid leukemia, with all 7 cases (100%) demonstrating shared clonal mutations in both the skin and BM. However, clonal relatedness was documented in one additional case that never had any BM involvement. Nevertheless, NPM1 mutations were identified in 7 of the 10 (70%) of these c-AML cases while one had KMT2A rearrangement and one showed inv(16). All 3 patients (100%) with Langerhans cell neoplasms, 2 patients with BPDCN (100%), and one of the 2 patients (50%) with other cutaneous dendritic cell neoplasms also demonstrated shared mutations between the skin and concurrent or subsequent myeloid neoplasms. Both BM and c-AML shared identical founding drivers, with a predominance of NPM1, DNMT3A, and translocations associated with monocytic differentiation, with common cutaneous-only mutations involving genes in the signal transduction and epigenetic pathways. Cutaneous histiocytic-dendritic neoplasms shared founding drivers in ASXL1, TET2, and/or SRSF2. However, in the Langerhans cell histiocytosis or histiocytic sarcoma cases, there exist recurrent secondary RAS pathway hits, whereas cutaneous BPDCN cases exhibit copy number or structural variants. These results enrich and broaden our understanding of clonally related cutaneous manifestations of myeloid neoplasms and further illuminate the highly diverse spectrum of morphologic and immunophenotypic features they exhibit.

Primary pulmonary Hodgkin's lymphoma mimicking granulomatosis with polyangiitis - a case report of diagnostic and therapeutic dilemmas.

Primary pulmonary Hodgkin's lymphoma (PPHL) is a rare subtype of lymphoma that comprises a small percentage of primary pulmonary lymphomas. Due to its rarity and nonspecific symptoms, PPHL often presents diagnostic challenges. This case report presents a unique case of PPHL mimicking granulomatosis with polyangiitis, emphasizing the difficulties encountered during the diagnostic process. A 53-year-old female presented with vague symptoms including weakness, oedema, dry cough, and nasal cavity ulceration. Laboratory investigations revealed elevated C-reactive protein levels, a white blood cell count with neutrophilia, and lymphopaenia. Initial treatment with oral corticosteroids for suspected polyangiitis yielded no response. The patient subsequently developed a low-grade fever and pruritic erythematous rash. Diagnostic procedures, including bronchial brush biopsy, bronchial washing, mediastinal lymph node biopsy, nasal cavity ulceration biopsy, and initial lung biopsy, were inconclusive and resulted in exclusion of granulomatosis with polyangiitis. A subsequent computed tomography scan indicated disease progression in the left lung. A lung biopsy revealed fibrotic tissue with nodules containing Hodgkin- Reed-Sternberg cells, leading to the final diagnosis of classic Hodgkin lymphoma, nodular sclerosis subtype. Positron emission tomography scan findings confirmed PPHL. The patient received multiple chemotherapeutic regimens, with brentuximab vedotin demonstrating efficacy as the sole effective treatment. This exceptional case of PPHL underscores the extensive diagnostic and therapeutic workup involving a multidisciplinary team of clinicians, radiologists, and pathologists. Increased awareness of PPHL and its distinctive features will aid in the diagnosis of similar cases in the future, benefitting both clinicians and pathologists.

Possible Concomitant Aggressive NK Cell Leukemia and EBV-positive T-cell lymphoma; Using the online beta version of WHO-HAEM5 and videoconferencing software to make diagnoses accessible in an emerging economy.

BACKGROUND: Using the World Health Organization Classification 5th edition (beta version online; WHO-HAEM5bv) in emerging economies is key to global healthcare equity. Although there may be ongoing updates, hesitancy in accepting and reporting these diagnoses in publication conflicts with the WHO's commitment to global accessibility. Aggressive NK cell leukemia (ANKL) and systemic EBV-positive T-cell lymphoma of childhood (SEBVTCL) with CD4-positive immunophenotype are both rare entities, are most described in Asians and East Asians, are associated with prior systemic chronic active EBV disease (CAEBV), and presentation with Hemophagocytic Lymphohistiocytosis (HLH). Recognizing and diagnosing any one of these entities requires not only training and experience in hematopathology, but good cooperation between clinical physicians and all areas of the laboratory. We describe a 30-year-old woman who presented to a Vietnam hospital and was rapidly diagnosed with ANKL, SEBVTCL, and HLH using WHO-HAEM5bv essential criteria, aided by expert consultation from a United States (US) board certified hematopathologist in real-time using video conferencing software. METHODS: Zoom™ videoconferencing software; Immunohistochemistry; flow cytometric immunophenotyping; polymerase chain reaction (PCR), Next Generation Sequencing (NGS). RESULTS: At the time of hospital admission, automated complete blood count (CBC) with differential count showed slight anemia, slight lymphocytosis, and moderate thrombocytopenia. HIV serology was negative. Whole blood PCR for EBV was positive showing 98,000 copies/ml. A lymph node biopsy revealed histology and immunohistochemistry consistent with the online beta version WHO-HAEM5 classification of SEBVTCL arising in CAEBV. Blood and bone marrow studies performed for staging revealed no histologic or immunohistochemical evidence of T-cell lymphoma in the bone marrow core, however, atypical blood smear lymphocyte morphology and blood immunophenotyping by flow cytometry were consistent with WHO-HAEM5 classification of ANKL. NGS revealed no evidence of genetic variant(s) associated with HLH in Vietnam. All laboratory studies were performed at Blood Transfusion Hematology Hospital (BTHH) in Ho Chi Minh City Vietnam. CONCLUSION: Although Vietnam, an emerging economy, currently lacks the laboratory infrastructure to more rigorously confirm a rare synchronous presentation of two distinct EBV-driven T/NK cell neoplasms, these two concomitant diagnoses were made using only laboratory techniques available in Vietnam with the help of WHO-HAEM5bv and real-time video consultation by a US hematopathologist.

Real-world routine diagnostic molecular analysis for TP53 mutational status is recommended over p53 immunohistochemistry in B-cell lymphomas.

Previous studies in patients with mature B-cell lymphomas (MBCL) have shown that pathogenic TP53 aberrations are associated with inferior chemotherapeutic efficacy and survival outcomes. In solid malignancies, p53 immunohistochemistry is commonly used as a surrogate marker to assess TP53 mutations, but this correlation is not yet well-established in lymphomas. This study evaluated the accuracy of p53 immunohistochemistry as a surrogate marker for TP53 mutational analysis in a large real-world patient cohort of 354 MBCL patients within routine diagnostic practice. For each case, p53 IHC was assigned to one of three categories: wild type (staining 1-50% of tumor cells with variable nuclear staining), abnormal complete absence or abnormal overexpression (strong and diffuse staining > 50% of tumor cells). Pathogenic variants of TP53 were identified with a targeted next generation sequencing (tNGS) panel. Wild type p53 expression was observed in 267 cases (75.4%), complete absence in twenty cases (5.7%) and the overexpression pattern in 67 cases (18.9%). tNGS identified a pathogenic TP53 mutation in 102 patients (29%). The overall accuracy of p53 IHC was 84.5% (95% CI 80.3-88.1), with a robust specificity of 92.1% (95% CI 88.0- 95.1), but a low sensitivity of 65.7% (95% CI 55.7-74.8). These results suggest that the performance of p53 IHC is insufficient as a surrogate marker for TP53 mutations in our real-world routine diagnostic workup of MBCL patients. By using p53 immunohistochemistry alone, there is a significant risk a TP53 mutation will be missed, resulting in misevaluation of a high-risk patient. Therefore, molecular analysis is recommended in all MBCL patients, especially for further development of risk-directed therapies based on TP53 mutation status.