Diagnostic issues in neuroendocrine neoplasms of the lung.

Bronchopulmonary neuroendocrine neoplasms (BP-NENs) account for approximately 30% of all NENs. Although BP-NENs and NENs of the gastroenteropancreatic organs (GEP-NENs) share morphological and molecular features, they differ in terms of their terminology and classification. Bronchopulmonary neuroendocrine tumors (BP-NETs) have classically been termed as carcinoid and grouped into typical (TC) and atypical carcinoid (AC) based on the presence or absence of necrosis and mitotic count. In the most recent World Health Organization (WHO) classification for NENs of endocrine organs (WHO 2022), BP-NETs-NET G1 and G2-are introduced as synonyms of TC and AC, respectively. However, the Ki-67 index, which defines the grade of NETs in digestive organs, is only discussed in the descriptive text and not included into the criteria for classification of BP-NENs. In addition, well-differentiated NENs with high mitotic counts which correspond to NET G3 in the GEP organ system are not defined. This review discusses the role of Ki-67 for a proper classification of BP-NETs/carcinoids.

The 2023 WHO updates on skin tumors: advances since the 2018 edition.

Pathology is pivotal in diagnosing skin tumors, and the precision of diagnosis is crucial to devise customized treatment plans and enhance patient care in dermatology. The latest edition of the World Health Organization's classification of skin tumors serves as a comprehensive compendium, summarizing and categorizing all recent advancements in both anatomical-pathological and molecular aspects of cutaneous neoplasms. Several relevant advances have been introduced and new entities have been described. While the fundamental structure of the classification remains unchanged, notable additions include three new sections aimed at providing a more exhaustive description of skin lesions: nail unit tumors, skin metastases, and genetic tumor syndromes associated with skin malignancies. Recent strides in molecular pathology have led to significant breakthroughs in decoding the underlying mechanisms of various skin tumors, ranging from adnexal neoplasms to hematolymphoid neoplasms, soft tissue tumors, and melanocytic lesions. Of particular importance is the evolution in our understanding of melanocytic neoplasms, with the introduction of the term "melanocytoma" reserved for lesions exhibiting "intermediate" biological behavior and characterized by specific molecular mutations. The pathologic diagnosis process integrates morphological, immunohistochemical, and molecular features, playing a crucial role in clinical decision-making. The WHO classification serves as a valuable tool in promoting multidisciplinarity in the management of cutaneous neoplasms with the aim of translating novel pathological discoveries into more effective treatments. This review aims to distill the major updates introduced by the new classification, providing a synthesis of the latest scientific insights.

Epidemiological Features of 4777 Cysts and Odontogenic Tumors Based on the 2022 WHO Classification.

OBJECTIVE: The epidemiology of cysts and odontogenic tumors is important for differential diagnosis and treatment strategies. We aimed to describe the epidemiological features of cysts and odontogenic tumors in the Chilean population using the current WHO classification. MATERIALS AND METHODS: We reviewed 22,914 biopsy requests received between January 1984 and September 2023 at the oral pathology department, School of Dentistry, Universidad Mayor, Santiago, Chile. Patients diagnosed with cysts of the jaws and odontogenic tumors were selected and information regarding age, sex, and location was recorded. RESULTS: 4226 (18.4%) were cysts, and 551 (2.4%) were odontogenic tumors, ranging from 2 to 97 years old. Males represented 54.4% and females 45.7% of the total sample. The most prevalent cysts were radicular cysts (58.6%), dentigerous cysts (17.9%), and odontogenic keratocysts (13.3%). The most prevalent odontogenic tumors were odontomas (40.1%) and conventional ameloblastoma (17.6%). CONCLUSIONS: Our study was the first retrospective analysis to determine the epidemiological features of both cysts and odontogenic tumors together, based on the 2022 WHO classification. This is relevant as it offers a potential basis for comprehensive comparisons of the epidemiological features of these entities, which could contribute to an accurate differential diagnosis, therefore, leading to more effective therapeutic interventions.

Understanding splenic B-cell lymphoma/leukaemia with prominent nucleoli: Diagnosis, underpinnings for disease classification and future directions.

The 5th edition of the WHO classification of haematolymphoid tumours (WHO-HAEM5) introduced a new category, splenic B-cell lymphoma/leukaemia with prominent nucleoli (SBLPN). The diagnostic entity B-cell prolymphocytic leukaemia (B-PLL) has been discontinued and the category of hairy cell leukaemia variant (HCLv) has been conceptually reframed. B-PLL and HCLv diagnoses were uncommon. Overlap existed between B-PLL and other indolent lymphomas like chronic lymphocytic leukaemia/small lymphocytic lymphoma (CLL/SLL). HCLv lacked consistent cytomorphological, immunophenotypic and genetic features. To address these issues, the WHO-HAEM5 classification has introduced SBLPN to serve as a temporary holding ground for entities that do not neatly fit into the existing classification. Cases previously classified as CD5-negative B-PLL and HCLv fall under the SBLPN category. Some splenic marginal zone lymphoma and splenic diffuse red pulp small B-cell lymphoma cases with higher number of medium or large nucleolated B cells would also be classified as SBLPN under the WHO-HAEM5. This review explores the rationale for discontinuing B-PLL and HCLv diagnoses. It then examines the concept of SBLPN, offers practical guidance for diagnosis and discusses future directions in classifying splenic B-cell lymphomas.

Imaging Features and World Health Organization Classification of Rare Breast Tumors.

Breast radiologists encounter unusual lesions, which may not be well described in the literature. Previously based on histologic and molecular classifications, the World Health Organization (WHO) classification of tumors has become increasingly multidisciplinary. Familiarity with imaging features and basic pathology of infrequent breast lesions, as well as their current classification according to the WHO, may help the radiologist evaluate biopsy results for concordance and help direct the management of uncommon breast lesions. This review article provides a case-based review of imaging features and WHO histologic classification of rare breast tumors.

Glioneuronal and neuronal tumors: A perspective.

Glioneuronal and neuronal tumors (GNTs) are slow-growing, lower-grade neuroepithelial tumors characterized by mature neuronal differentiation and, less consistently, glial differentiation. Their identification has traditionally relied on histological proof of neuronal differentiation, reflecting the well-differentiated nature of GNTs. However, after discovering genetic alterations in GNTs, particularly those in the MAP-kinase pathway, it became evident that histological diagnoses do not always correlate with genetic alterations and vice versa. Therefore, molecular-based classification is now warranted since several inhibitors targeting the MAP-kinase pathway are available. The World Health Organization classification published in 2021 applied DNA methylation profiling to segregate low-grade neuroepithelial tumors. As GNTs are essentially indolent, radical resection and unnecessary chemoradiotherapy may be more harmful than beneficial for patients. Preserving tumor tissue for potential future treatments is more important for patients with GNTs.

Impact on natural history of atypical meningioma after changes in 2016 edition of the world health organization (WHO) classification of central nervous system tumors: a literature review.

Meningiomas and their WHO histological diagnostic criteria is complex, especially for grade 2 tumors presenting a interobserver discordance as high as 12.2%. The 2016 edition of the WHO Classification of CNS tumors recommended brain invasion as a stand-alone grading criterion for diagnosing an atypical grade 2 meningioma (AM). To provide an overview of the classification of 2016 WHO impact on the natural history of atypical meningioma (AM) relative to previous classification. To achieve this goal, we selected articles from the period 2017-2024 in Medline search on atypical meningiomas and analyzed them after following the following criteria: 1) reports with confirmed histopathological diagnosis according to WHO 2016 and or 2021 criteria; 2) series and case reports; 3) detailed and individualized clinical outcomes for AM; and 4) papers written in English; after that a total of 3445 patients reported in 67 manuscripts from worldwide centers from 2017 to March 2024 were analyzed. The patient's age at the time of surgery ranged from 1 month to 97 years (mean 52.28 ± 18.7 years). The most common tumor site was the convexity, accounting for 67.8%, followed by the skull base in 30.6%, ventricle in 1%, and spine in 0.6%; Gross total resection (GTR) was performed in 71.25% and subtotal resection (STR) in 28.75%; 1021 patients (29.63%) underwent adjuvant radiotherapy, and 22 patients (0.6%) were treated with adjuvant chemotherapy; tumor recurrence was reported in 1221 patients (35.44%) and 859 deaths (24.93%). 1) AM prevalence in females; 2) AM age distribution similar to the distribution of meningiomas in general; 3) AM recurrence rate of 35.44%, despite the high rate of GTR, which was higher than previously reported; 4) deepening knowledge in molecular mechanism of tumor progression will provide alternative therapeutic approaches for AM.

A High-Grade Glioma, Not Elsewhere Classified in an Older Adult with Discordant Genetic and Epigenetic Analyses.

The World Health Organization's (WHO) classification of central nervous system (CNS) tumors is continually being refined to improve the existing diagnostic criteria for high-grade gliomas (HGGs), including glioblastoma. In 2021, advances in molecular analyses and DNA methylation profiling were incorporated to expand upon the diagnostic criteria for HGG, including the introduction of high-grade astrocytoma with piloid features (HGAP), a new tumor entity for which a match to the HGAP class in DNA methylation profiling is an essential criterion. We present an equivocal case of a 72-year-old male with an HGG exhibiting features of both HGAP and glioblastoma, but which did not conform to any existing 2021 WHO classification of CNS tumor entities. This "no match" in DNA methylation profiling resulted in a final diagnosis of HGG not elsewhere classified (NEC), for which standard treatment options do not exist.

Grading and staging for pituitary neuroendocrine tumors.

Pituitary adenoma/pituitary neuroendocrine tumors (PitNETs) are the second most common primary intracranial tumor and the most frequent neuroendocrine tumors/neoplasms of the human body. Thus, they are one of the most frequent diagnoses in neuropathologist's practise. 2022 5th edition WHO Classification of Endocrine and Neuroendocrine Tumors does not support a grading and/or staging system for PitNETs and argues that histological typing and subtyping are more robust than proliferation rate and invasiveness to stratify tumors. Numerous studies suggest the existence of clinically relevant molecular subgroups encouraging an integrated histo-molecular approach to the diagnosis of PitNETs to deepen the understanding of their biology and overcome the unresolved problem of grading system. The present review illustrates the main issues involved in establishing a grading and a staging system, as well as alternative systems validated by independent series to date. The state of art of the current histological and molecular markers is detailed, demonstrating that a standardized and reproducible clinico-pathological approach, combined with the integration of molecular data may help build a workflow to refine the definition of PitNETs with 'malignant potential' and most importantly, avoid delay in patient treatment. Next molecular studied are needed to validate an integrated histo-molecular grading for PitNETs.

[Acute myeloid leukemia with mutated RUNX1 at the university hospitals of Strasbourg]. / Étude rétrospective des leucémies aiguës myéloïdes mutées RUNX1 aux hôpitaux ­universitaires de Strasbourg.

RUNX1 is essential during human hematopoiesis. Numerous RUNX1 deregulations have been described, including translocations and germline or somatic mutations. Recurrent de novo RUNX1 mutations in acute myeloid leukemias (AML) prompted the creation of a provisional entity of AML with mutated RUNX1 in the 2016 WHO. In addition, recent genomic studies underlined rare AML patients with plasmacytoid dendritic cell (pDC) expansion and high RUNX1 mutations frequency. To better characterized AML with RUNX1 mutations, we retrospectively investigated a cohort of 32 patients diagnosed at Strasbourg University Hospital. Detailed clinical and biological features were aggregated. The presence of a pDC contingent was assessed by cytology and flow cytometry. In our cohort, no common features were identified either in term of cytology, stage of leukemia arrest or mutational features. Based on our observations, mutated RUNX1 AMLs do not appear to be a distinct AML entity. The new 2022 WHO classification includes AML with mutated RUNX1 within AML myelodysplasia-related category. We also identified within our cohort a patient whose AML fulfilled AML-pDC criteria, a rare and newly included entity in the last WHO classification.

Comparison of ultrasound findings of papillary thyroid carcinoma subtypes based on the 2022 WHO classification of thyroid neoplasms.

Purpose: The present study aimed to analyze and compare sonographic features of papillary thyroid carcinoma (PTC) subtypes to determine whether ultrasound (US) may aid in differentiating particular subtypes. Methods: This retrospective study enrolled 133 patients diagnosed with 142 histopathologically proven PTCs as per the fifth edition of the World Health Organization classification of thyroid neoplasms between January 2013 and May 2023. US features based on the American College of Radiology and European Thyroid Imaging and Reporting Data Systems (TIRADS), and histopathological characteristics of nodules were assessed and compared. Results: Histopathological analysis yielded 55 (38.7%) classic PTC, 32 (22.5%) invasive encapsulated follicular variant (IEFV) PTC, 20 (14.1%) oncocytic subtype, 14 (9.9%) non-invasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP), 11 (7.8%) infiltrative follicular subtype, 7 (4.9%) tall cell subtype, 2 (1.4%) solid subtype, and 1 (0.7%) diffuse sclerosing subtype. The US findings indicating malignancy, such as taller-than-wide shape, irregular margins, echogenic foci, and higher TIRADS categories, were more frequently demonstrated in nodules with classic PTC and the tall cell subtype, in line with their histopathological features. Conversely, IEFV-PTC and NIFTP rarely exhibited these high-risk sonographic features. US appearance of the oncocytic subtype more frequently overlapped with IEFV-PTC, yet hypo/very hypoechoic nodules with larger nodular diameters and higher TIRADS scores may favor the diagnosis of this subtype. Conclusion: US features of certain subtypes may guide the differential diagnosis regarding shape, margin, echogenic foci, and TIRADS category of nodules; however, definitive subtyping is not yet possible using US images alone.

Impact of Reclassification of Oncocytic and Follicular Thyroid Carcinoma by the 2022 WHO Classification.

BACKGROUND: The 2022 WHO Classification categorizes oncocytic (OTC) and follicular thyroid carcinoma (FTC) based on the degree of capsular and vascular invasion into minimally invasive (MI), encapsulated angioinvasive (EA) and widely invasive tumors (WI). While associations with clinical outcomes have been studied extensively in FTC, robust clinical data are lacking for OTC. We aimed to investigate the impact of the reclassification of OTC and FTC by the 2022 WHO Classification on clinical outcomes. METHODS: All adult OTC and FTC patients treated at the Erasmus MC (the Netherlands) between 2000 and 2016 were retrospectively included. All tumors were extensively revised by two independent pathologists, facilitated by Palga: Dutch Pathology Databank. Kaplan-Meier curves were used to study the association of the 2004 and 2022 WHO Classification with overall survival (OS), disease-specific survival (DSS), recurrence-free survival (RFS) and radioactive iodine (RAI) refractory disease. RESULTS: Fifty-two OTC and 89 FTC patients were included, of which 15 (28.8%) OTC and 34 (38.2%) FTC tumors were reclassified as EAOTC or EAFTC. The 2022 WHO Classification substantially improved risk stratification in both subtypes for DSS, compared with the 2004 edition. Ten-year DSS rates were 100% for MIOTC, 92.9% for EAOTC and 56.5% for WIOTC, compared to 100% (MIOTC) and 64.2% (WIOTC) following the 2004 WHO Classification. For FTC and RAI-refractory disease, similar trends were observed. CONCLUSION: Classification of OTC and FTC into three subcategories as defined by the 2022 WHO Classification substantially improves discrimination between low, intermediate and high risk patients, especially for DSS and RAI-refractory disease.

The fifth edition of the WHO-Classification - what is new for cutaneous lymphomas?

The recently published 5th edition of the "World Health Organization classification of hematolymphoid tumors: lymphoid neoplasms" provides a hierarchical reorganization. In general, new (definitive) entities as well as tumor-like lesions were included. Primary cutaneous B-cell lymphomas (CBCL) received a thorough review. A new class/family of cutaneous follicle center lymphomas was defined. Primary cutaneous marginal zone lymphoma is now presented as a separate entity independent from extranodal marginal zone lymphoma of mucosa-associated lymphoid tissue. In primary cutaneous T-cell lymphoma, former provisional entities were upgraded to definite entities. Sézary Syndrome was sorted into the class/family of mature T-cell and NK-cell leukemias. Additionally, a newly formed entity of primary cutaneous peripheral T-cell lymphoma, NOS was created for CTCL entities that do not fit into the already described CTCL entities. The increasing importance of genomic and molecular data has already been recognized in classifying leukemias and systemic lymphomas. However, in PCL the genomic landscape has not yet been fully described and validated. Therefore, future research is necessary to describe the genomic and molecular mechanisms underlying the disease entities more clearly. This would both meet a diagnostic need and valuably contribute to future classification schemes.

Pitfalls of cytological diagnosis of tumours of the pancreaticobiliary tract.

The recent introduction of the WHO cytology classification of pancreatobiliary tumours aimed to improve the diagnosis and management of these tumours. The present paper briefly describes the methods of diagnosis. Emphasis is then put on a detailed comparison of the previous Papanicolaou classification and the new WHO classification and description of the changes brought about by the introduction of the WHO classification. In the last part of the paper, we present interesting cases from our practice illustrating possible diagnostic pitfalls of cytological evaluation.

WHO/ICC Classification for Myelodysplastic Neoplasms/Syndromes Performs Better for Subtype Cytomorphological Diagnosis?

The International Consensus Classification of Myeloid Neoplasms and Acute Leukemias (ICC) and the 5th edition of the WHO classification (WHO 2022) have refined the diagnosis of myelodysplastic syndromes (MDS). Both classifications segregate MDS subtypes based on molecular or cytogenetic findings but rely on the subjective assessment of blast cell percentage and dysplasia in hematopoietic cell lineages. This study aimed to evaluate interobserver concordance among 13 cytomorphologists from eight hospitals in assessing blast percentages and dysplastic features in 44 MDS patients. The study found fair interobserver agreement for the PB blast percentage and moderate agreement for the BM blast percentage, with the best concordance in cases with <5% BM blasts and >10% BM blasts. Monocyte count agreement was fair, and dysplasia assessment showed moderate concordance for megakaryocytic lineage but lower concordance for erythroid and granulocytic lineages. Overall, interobserver concordance for MDS subtypes was moderate across all classifications, with slightly better results for WHO 2022. These findings highlight the ongoing need for morphological evaluation in MDS diagnosis despite advances in genetic and molecular techniques. The study supports the blast percentage ranges established by the ICC but suggests refining BM blast cutoffs. Given the moderate interobserver concordance, a unified classification approach for MDS is recommended.

Overview of histiocytic and dendritic disorders by the 5th version of WHO Classifi cation of Hematolymphoid Tumours from 2022.

BACKGROUND: Histiocytoses are rare disorders characterized by the accumulation of macrophages, dendritic cells, or monocyte-derived cells in various tissues and organs of children and adults, with a wide range of clinical manifestations, presentations, and histology. The histiocytoses are classified according to the WHO Classification, the last version of which was published in 2022, or according to the Histiocyte Society Classification, with the last version published in 2016. PURPOSE: This text provides an overview of histiocytoses as described in the WHO Classification 2022.

Cutaneous Lymphoma in a Tertiary Skin Hospital and Referral Centre in Nepal.

BACKGROUND: Primary cutaneous lymphomas are a distinct group of rare lymphoid neoplasms with absence of extracutaneous lymphomas at the time of presentation. They are rare in Nepal and no data on cutaneous lymphoma have been published from this country till date. METHODS: This retrospective study included 15 cases of cutaneous lymphomas retrieved from the records of department of Dermatopathology, DI Skin Hospital and Referral Centre, Bansbari, Kathmandu, Nepal. Patients were diagnosed according to the current WHO classification for cutaneous lymphoma. RESULTS: A total of 15 cases were studied with median age of 45 years (range: 22 to 81 years) and male to female ratio of 1.5:1. Primary cutaneous lymphomas constituted 13 cases out of 15 and the most common type of cutaneous lymphoma was mycosis fungoides and variants 5 (33%), followed by CD30 positive primary cutaneous anaplastic large cell lymphoma constituting 2 (13%). T-cell cutaneous lymphoma constituted 13 (87%) and B-cell cutaneous lymphoma 2 (13%). CONCLUSIONS: Cutaneous T-cell lymphomas were more frequent than cutaneous B-cell lymphomas in Nepalese patients. Mycosis fungoides and variants are commonest type of primary cutaneous lymphomas.

Pediatric lymphoproliferative disorders associated with inborn errors of immunity.

Both non-malignant and malignant lymphoproliferative disorders (LPD) are commonly seen in patients with inborn errors of immunity (IEI), which may be the presenting manifestations or may develop during the IEI disease course. Here we review the clinical, histopathological, and molecular features of benign and malignant LPD associated with IEI and recognize the diagnostic challenges.