World Health Organization Classification Of Tumors Research Articles

Radiologic-Pathologic Correlation of Cardiac Tumors: Updated 2021 WHO Tumor Classification.

Cardiac tumors, although rare, carry high morbidity and mortality rates. They are commonly first identified either at echocardiography or incidentally at thoracoabdominal CT performed for noncardiac indications. Multimodality imaging often helps to determine the cause of these masses. Cardiac tumors comprise a distinct category in the World Health Organization (WHO) classification of tumors. The updated 2021 WHO classification of tumors of the heart incorporates new entities and reclassifies others. In the new classification system, papillary fibroelastoma is recognized as the most common primary cardiac neoplasm. Pseudotumors including thrombi and anatomic variants (eg, crista terminalis, accessory papillary muscles, or coumadin ridge) are the most common intracardiac masses identified at imaging. Cardiac metastases are substantially more common than primary cardiac tumors. Although echocardiography is usually the first examination, cardiac MRI is the modality of choice for the identification and characterization of cardiac masses. Cardiac CT serves as an alternative in patients who cannot tolerate MRI. PET performed with CT or MRI enables metabolic characterization of malignant cardiac masses. Imaging individualized to a particular tumor type and location is crucial for treatment planning. Tumor terminology changes as our understanding of tumor biology and behavior evolves. Familiarity with the updated classification system is important as a guide to radiologic investigation and medical or surgical management. ©RSNA, 2024 Supplemental material is available for this article.

What is new in the 5th edition of the World Health Organization classification of mature B and T/NK cell tumors and stromal neoplasms?

The classification of tumors is essential in the diagnosis and clinical management of patients with malignant neoplasms. The World Health Organization (WHO) provides a globally applicable classification scheme of neoplasms and it was updated several times. In this review, we briefly outline the cornerstones of the upcoming 5th edition of the World Health Organization Classification of Haematolymphoid Tumours on lymphoid neoplasms. As is adopted throughout the 5th edition of the WHO classification of tumors of all organ systems, entities are listed by a hierarchical system. For the first time, tumor-like lesions have been included in the classification, and modifications of nomenclature for some entities, revisions of diagnostic criteria or subtypes, deletion of certain entities, and introduction of new entities are presented along with mesenchymal lesions specific to the stroma of lymph nodes and the spleen. In addition to specific outlines on constitutional and somatic genetic changes associated with given entities, a separate chapter on germline predisposition syndromes related to hematologic neoplasms has been added.

Spinal Ependymomas: An Updated WHO Classification and a Narrative Review.

Ependymomas are neuroepithelial tumors that develop from ependymal cells found in the brain parenchyma and can spread to any part of the spinal cord. Three to six percent of all malignanciesaffecting the central nervous system (CNS) are ependymomas. Even the most talented surgeons are challenged by spinal cord ependymomas; as a result, research into this clinical phenomenon should continue. Since 1979, the World Health Organization (WHO) has published a classification and grading system for CNS malignancies to ensure consistent diagnostic standards worldwide. The WHO prepared an update on these tumors, paying particular attention to molecular techniques to categorize the therapeutic management of each patient with greater accuracy and clarity.We thoroughly reviewedthe literature on the epidemiology, etiology, diagnosis, and treatment of spinal ependymomas since there has not been a recent review of these tumors. This included modifications to the 2021 WHO Classification of Tumors of the Central Nervous System.

The rationale for the development and publication of the World Health Organization reporting systems for cytopathology and a brief overview of the first editions of the lung and pancreaticobiliary systems.

The International Academy of Cytology has joined with the International Agency for Research on Cancer and the World Health Organization (WHO) to develop international systems for reporting the cytopathology of lung, pancreas and biliary tract, lymph nodes, soft tissue, liver, breast, and kidney and adrenal gland. The WHO recently published the reporting systems for lung and pancreaticobiliary cytopathology. The objectives of this collaboration are to standardize the reporting of cytopathology; improve the quality of reporting by establishing the key diagnostic cytopathological features of entities and neoplasms; provide detailed best-practice guidelines in sampling techniques, specimen handling and processing, and the use of ancillary techniques; and facilitate communication between cytopathologists and clinicians to improve patient care. Each WHO system has defined specific categories and terminology for reporting cytopathology, and each category has an estimated risk of malignancy as far as the current literature allows and a suggested diagnostic management algorithm to assist clinicians. The WHO systems recognize that local medical and pathology infrastructure will vary, particularly in low-income and middle-income countries, and the WHO systems and their diagnostic management recommendations have been developed to allow them to be applied worldwide in all resource settings. The process of the selection of editors and authors and the writing and editing responsibilities has used the same model as that used for the fifth edition WHO Classification of Tumours, to which the WHO cytopathology systems are directly linked. This review provides the rationale and history of this joint International Academy of Cytology, International Agency for Research on Cancer, and WHO cytopathology project and a brief overview of the WHO reporting systems for lung and pancreaticobiliary cytopathology.

Neuroimaging of pediatric tumors of the sellar region-A review in light of the 2021 WHO classification of tumors of the central nervous system.

Sellar/suprasellar tumors comprise about 10% of all pediatric Central Nervous System (CNS) tumors and include a wide variety of entities, with different cellular origins and distinctive histological and radiological findings, demanding customized neuroimaging protocols for appropriate diagnosis and management. The 5th edition of the World Health Organization (WHO) classification of CNS tumors unprecedently incorporated both histologic and molecular alterations into a common diagnostic framework, with a great impact in tumor classification and grading. Based on the current understanding of the clinical, molecular, and morphological features of CNS neoplasms, there have been additions of new tumor types and modifications of existing ones in the latest WHO tumor classification. In the specific case of sellar/suprasellar tumors, changes include for example separation of adamantinomatous and papillary craniopharyngiomas, now classified as distinct tumor types. Nevertheless, although the current molecular landscape is the fundamental driving force to the new WHO CNS tumor classification, the imaging profile of sellar/suprasellar tumors remains largely unexplored, particularly in the pediatric population. In this review, we aim to provide an essential pathological update to better understand the way sellar/suprasellar tumors are currently classified, with a focus on the pediatric population. Furthermore, we intend to present the neuroimaging features that may assist in the differential diagnosis, surgical planning, adjuvant/neoadjuvant therapy, and follow-up of this group of tumors in children.

Phyllodes tumour evidence gaps mapped from the 5th edition of the WHO classification of tumours of the breast.

Breast phyllodes tumours (PTs) are a rare subset of fibroepithelial neoplasms categorised into benign, borderline, and malignant grades according to the World Health Organization (WHO) Classification of Tumours (WCTs). In this report, we developed an evidence gap map (EGM) based on the literature cited in the PT chapter of the 5th edition of the breast WCT in order to identify knowledge and research gaps in PT. A framework was first established where the dimensions of the EGM were defined as categories of tumour descriptors, tumour types, and evidence levels. Citations were collected into a Microsoft Excel form and imported into EPPI-reviewer to produce the EGM. The EGM showed that the "Histopathology" and "Pathogenesis" sections contained the most citations, the majority being of low-level evidence. The highest number of citations considered of moderate-level evidence were found in the "Histopathology" section. There was no high-level evidence cited in this chapter. The "Localisation", "Aetiology", and "Staging" sections had the fewest citations. This EGM provides a visual representation of the cited literature in the PT chapter of the breast WCT, revealing the lack of high-level evidence citations. There is an uneven distribution of references, probably due to citation practices. Pockets of low-level evidence are highlighted, possibly related to referencing habits, lack of relevant research, or the belief that the information presented is standard accepted fact, without the need for specific citations. Future work needs to bridge evidence gaps and broaden citations beyond those in the latest WCT.

World health organization classification of bone tumors (fifth edition): What a radiologist needs to know?

Since 1967, the World Health Organization (WHO) classification of tumors is regarded as a reference standard and practical guide and provides a precious resource not only for the histopathologists and oncosurgeons but also for the radiologists involved in cancer care. Primary bone tumors are a rare and heterogeneous group of neoplasms that have a broad spectrum of morphological, biological, genetic, and radiological features. Appropriate imaging workup and accurate histopathological diagnosis are crucial for appropriate management and prognostication. The fourth edition of the WHO classification of tumors of soft tissue and bone was introduced in 2013. In the past 7 years, there have been considerable advances in the understanding of this large and diverse group of tumors. With technological advances and the introduction of new molecular and genetic data about some bone tumors, there has been reorganization in the classification and introduction of a few new entities. The new WHO classification of soft tissue and bone tumors introduced in 2020 (fifth edition) has made essential refinements in the classification and has also introduced many new entities. Newly identified genetic alterations and corresponding immunohistochemical markers are included in the new classification, and this has helped in the reclassification of the existing tumor entities. These novel genetic alterations not only help in prognostication but are a target for potential therapeutic options which can bring a paradigm shift in the chemotherapeutic regimen for these entities in the future. The sole basis for the classification of bone tumors is histopathological. Although radiologists are not expected to know about the exquisite pathological details of bone tumors, a broad knowledge of the recent updates, including the reclassification of a few entities or the introduction of some, is vital for narrowing the differentials in imaging. A multidisciplinary approach including an orthopedic oncologist, radiologist, pathologist, surgical, and medical oncologist is required for accurate diagnosis and management of primary bone tumors. We hereby present a simplified review for the radiologists comprising the relevant details of the updates in bone tumors along with a simplified diagnostic algorithm to characterize these lesions.

WES data from 286 diffuse gliomas under the 2021 WHO Classification of Tumors of the Central Nervous System

Diffuse gliomas (DGs) are the most common and lethal primary neoplasms in the central nervous system. The latest 2021 World Health Organization (WHO) Classification of Tumors of the Central Nervous System (CNS) was published in 2021, immensely changing the approach to diagnosis and decision making. As a part of the Chinese Glioma Genome Atlas (CGGA) project, our aim was to provide genomic profiling of gliomas in a Chinese cohort. Two hundred eighty six gliomas with different grades were collected over the last decade. Using the Illumina HiSeq platform, over 75.8 million high-quality 150 bp paired-end reads were generated per sample, yielding a total of 43.4 billion reads. We also collected each patient’s clinical and pathological information and used it to annotate their genetic data. All patients were diagnosed and classified by neuro-pathologist under the 2021 WHO classification. This dataset provides an important reference for researchers and will significantly advance our understanding of gliomas.

Changes to pediatric brain tumors in 2021 World Health Organization classification of tumors of the central nervous system.

New tumor types are continuously being described with advances in molecular testing and genomic analysis resulting in better prognostics, new targeted therapy options and improved patient outcomes. As a result of these advances, pathological classification of tumors is periodically updated with new editions of the World Health Organization (WHO) Classification of Tumors books. In 2021, WHO Classification of Tumors of the Central Nervous System, 5th edition (CNS5), was published with major changes in pediatric brain tumors officially recognized including pediatric gliomas being separated from adult gliomas, ependymomas being categorized based on anatomical compartment and many new tumor types, most of them seen in children. Additional general changes, such as tumor grading now being done within tumor types rather than across entities and changes in definition of glioblastoma, are also relevant to pediatric neuro-oncology practice. The purpose of this manuscript is to highlight the major changes in pediatric brain tumors in CNS5 most relevant to radiologists. Additionally, brief descriptions of newly recognized entities will be presented with a focus on imaging findings.

Frontiers in Breast Pathology.

Frontiers in Breast Pathology.

Major Changes in 2021 World Health Organization Classification of Central Nervous System Tumors.

The World Health Organization (WHO) published the fifth edition of the WHO Classification of Tumors of the Central Nervous System (WHO CNS5) in 2021, as an update of the WHO central nervous system (CNS) classification system published in 2016. WHO CNS5 was drafted on the basis of recommendations from the Consortium to Inform Molecular and Practical Approaches to CNS Tumor Taxonomy (cIMPACT-NOW) and expounds the classification scheme of the previous edition, which emphasized the importance of genetic and molecular changes in the characteristics of CNS tumors. Multiple newly recognized tumor types, including those for which there is limited knowledge regarding neuroimaging features, are detailed in WHO CNS5. The authors describe the major changes introduced in WHO CNS5, including revisions to tumor nomenclature. For example, WHO grade IV tumors in the fourth edition are equivalent to CNS WHO grade 4 tumors in the fifth edition, and diffuse midline glioma, H3 K27M-mutant, is equivalent to midline glioma, H3 K27-altered. With regard to tumor typing, isocitrate dehydrogenase (IDH)-mutant glioblastoma has been modified to IDH-mutant astrocytoma. In tumor grading, IDH-mutant astrocytomas are now graded according to the presence or absence of homozygous CDKN2A/B deletion. Moreover, the molecular mechanisms of tumorigenesis, as well as the clinical characteristics and imaging features of the tumor types newly recognized in WHO CNS5, are summarized. Given that WHO CNS5 has become the foundation for daily practice, radiologists need to be familiar with this new edition of the WHO CNS tumor classification system. Online supplemental material and the slide presentation from the RSNA Annual Meeting are available for this article. ©RSNA, 2022.

WHO 2022 landscape of papillary and chromophobe renal cell carcinoma.

The 5th edition of the WHO Classification of Tumours of the Urinary and Male Genital Systems contains relevant revisions and introduces a group of molecularly defined renal tumour subtypes. Herein we present the World Health Organization (WHO) 2022 perspectives on papillary and chromophobe renal cell carcinoma with emphasis on their evolving classification, differential diagnosis, and emerging entities. The WHO 2022 classification eliminated the type 1/2 papillary renal cell carcinoma (pRCC) subcategorization, given the recognition of frequent mixed tumour phenotypes and the existence of entities with a different molecular background within the type 2 pRCC category. Additionally, emerging entities such as biphasic squamoid alveolar RCC, biphasic hyalinising psammomatous RCC, papillary renal neoplasm with reverse polarity, and Warthin-like pRCC are included as part of the pRCC spectrum, while additional morphological and molecular data are being gathered. In addition to oncocytomas and chromophobe renal cell carcinoma (chRCC), a category of 'other oncocytic tumours' with oncocytoma/chRCC-like features has been introduced, including emerging entities, most with TSC/mTOR pathway alterations (eosinophilic vacuolated tumour and so-called 'low-grade' oncocytic tumour), deserving additional research. Eosinophilic solid and cystic RCC was accepted as a new and independent tumour entity. Finally, a highly reproducible and clinically relevant universal grading system for chRCC is still missing and is another niche of ongoing investigation. This review discusses these developments and highlights emerging morphological and molecular data relevant for the classification of renal cell carcinoma.

The World Health Organization Classification of Tumors and External Quality Assurance for Immunohistochemistry and Molecular Pathology.

This article is based on a talk given by the lead author at the Eigth Annual Princeton Integrated Pathology Symposium: Breast Pathology, on Sunday, April 11, 2021. To show how the World Health Organization (WHO) Classification of Tumours links to the requirements for quality assurance in breast pathology, including both immunohistochemistry and molecular pathology. The WHO Classification of Tumours 5th edition Breast Tumours entries formed the basis of the talk, together with guidance published by the International Quality Network for Pathology. The WHO Classification of Tumours provides a definitive set of international standards for tumor diagnosis contributed by experts, based on available clinical and research evidence. Techniques used in pathology need internal and external quality assurance to ensure accurate reports for patient management.

Characterizing malignant transformation in patients with IDH-mutant glioma.

2065 Background: Gliomas, which constitute the majority of primary brain cancers in adults, are assigned to a particular grade based on histological and molecular criteria set forth by the World Health Organization (WHO). A subset of initially low grade glioma patients transition to a higher grade at recurrence through a process known as malignant transformation (MT). Despite its significant implications on clinical prognosis, MT remains a poorly understood phenomenon in regards to its incidence rates, effects on survival, and potential prognostic factors. Our study aims to elucidate MT in patients that possess a mutation in the isocitrate dehydrogenase ( IDH) gene, one of the most common genetic alterations in gliomas. Methods: All known IDH mutant glioma patients, seen at UCLA between 1986 and 2022, who received at least 1 repeat resection for presumed recurrent disease were included. Based on surgical pathology reports, patients were categorized into MT and non-transforming progression groups, and further stratified by diagnosis in compliance with the 2016 WHO Classification of Tumors of the Central Nervous System. Relevant clinical information, including patient demographics, survival data, tumor microscopic descriptions, and magnetic resonance imaging, was accessed via electronic medical records. Kaplan Meier analyses were conducted to evaluate the predictive power of various clinical, pathological, and radiological markers. Results: Of 724 total IDH mutant patients screened, 253 received a second surgery and were thus incorporated in this study. Among the 196 patients with lower grade pathologies capable of MT, 129 (65.8%) progressed to a higher grade at recurrence while 71 (36.2%) did not. By diagnosis, the incidence rates of MT for initial grade 2 astrocytomas, grade 3 astrocytomas, and grade 2 oligodendrogliomas were determined to be 74.7%, 48.9%, and 66.1%, respectively. MT was associated with worse overall survival and post-recurrence survival compared to non-transformation in astrocytomas, a trend not seen in oligodendrogliomas. Across all relevant diagnoses, a subset of 36 MT patients did not receive treatment in the interval between initial and recurrent surgery, demonstrating the existence of spontaneously occurring MT. Furthermore, consolidating data from pathology and MRI reports revealed that a greater extent of abnormal molecular characteristics at initial diagnosis and earlier post-operative contrast enhancement may predict MT. Conclusions: These results highlight the distinct nature of gliomas that undergo MT, particularly in tumors of astrocytic differentiation. Considering its adverse impact on clinical outcome, understanding and anticipating this phenomenon is instrumental for the determination of optimal treatment among glioma patients.

Neuroendocrine Neoplasms of the Breast: The Latest WHO Classification and Review of the Literature.

Simple SummaryBreast tumors exhibiting neuroendocrine differentiation are a heterogeneous group of tumors that have been variously defined in previous World Health Organization (WHO) classifications. In the WHO Classification of Tumours, 5th edition, neuroendocrine tumors (NETs) and neuroendocrine carcinomas (NECs) of the breast, both of which are invasive cancers, are classified as neuroendocrine neoplasms (NENs) of the breast. However, the clinical significance of NE differentiation in breast cancers, especially in NETs of the breast, is not yet fully understood, and a large overlap appears to exist between breast cancers showing NE differentiation and invasive breast cancer of no special type (IBC-NST). While breast NECs show distinct clinical and morphological features, diagnosis of NETs based on the morphological characteristics alone can be challenging; one reason is that breast NETs do not necessarily have the same morphological characteristics as those of NENs arising in other organs. Thus, the heterogeneity of breast tumors with neuroendocrine differentiation and the changes in their classifications over the years have left many open issues that still need to be resolved. In this review, we shall summarize the history of breast “NENs,” including of mixed types of tumors and the characteristics of these tumors, and discuss their differences from NENs arising in other organs.Breast tumors with neuroendocrine (NE) differentiation comprise an uncommon and heterogeneous group of tumors, including invasive breast cancer of no special type (IBC-NST) with NE features, neuroendocrine tumors (NETs), and neuroendocrine carcinoma (NEC). The most recent World Health Organization (WHO) classification in 2019 defined neuroendocrine neoplasms (NENs) of the breast (Br-NENs) as tumors in which >90% of cells show histological evidence of NE differentiation, including NETs (low-grade tumors) and NEC (high-grade). Due to the low prevalence of these tumors and successive changes in their diagnostic criteria over the years, only limited evidence of these tumors exists, derived mainly from case reports and retrospective case series. Breast tumors with NE differentiation are usually treated like the more commonly occurring IBC-NSTs. Immunohistochemistry (IHC) of breast tumors with NE differentiation usually shows a hormone receptor (HR)-positive and human epidermal growth factor type 2 (HER2)-negative profile, so that hormonal therapy with cyclin-dependent kinase (CDK)4/6 inhibitors or other targeted agents would be reasonable treatment options. Herein, we present a review of the literature on breast tumors with NE differentiation as defined in the latest WHO 2019 classification, and discuss the clinical management of these tumors.

MPC-17 2021 WHO Classification of Tumors of the CNS, 5th ed

The grading of gliomas based on histological features has been a subject of debate for several decades. While the traditional grading system has failed to stratify the risk of IDH-mutant astrocytoma, canonical histological and proliferative markers may be applicable to the risk stratification of IDH-wildtype astrocytoma. Numerous studies have examined molecular markers to obtain more clinically relevant information that will improve the risk stratification of gliomas. The CDKN2A/B homozygous deletion for IDH-mutant astrocytoma and the following three criteria for IDH-wildtype astrocytoma: the concurrent gain of whole chromosome 7 and loss of whole chromosome 10, TERT promoter mutations, and EGFR amplification, were identified as independent molecular markers of the worst clinical outcomes. Therefore, the 2021 World Health Organization (WHO) Classification of Tumors of the Central Nervous System adopted these molecular markers into the revised grading criteria of IDH-mutant and -wildtype astrocytoma respectively, as a grading system within tumor types. For diffuse gliomas in children, molecular alteration-based classification was adopted, dividing low-grade and high-grade subcategories. New tumor types and subtypes were introduced, some based on DNA methylation profiling. To achieve this novel classification in a resource-limited setting, an integrated diagnosis combining clinical, histological, and molecular information became more important.

Updated WHO classification of tumors of the breast

In the fifth edition of the World Health Organization (WHO) classification of tumors of the breast, the histological features of the lesions continue to form the basis of the classification; however, molecular pathology nowadays provides approaches for improved diagnostics and prediction of prognosis and treatment response, which have been incorporated into the update of the classification. The most important changes are presented, which include changes in the histological classification of invasive carcinomas, the subtyping of lobular carcinoma in situ (LCIS) and the dignity criteria of phyllodes tumors.

Breast cancer detection by dedicated breast positron emission tomography according to the World Health Organization classification of breast tumors

ObjectiveConsidering the difficulty in detecting primary breast cancers using whole-body positron emission tomography (WBPET) owing to its limited spatial resolution, we aimed to evaluate the detectability of breast cancer by ring-type dedicated breast PET (DbPET) on the World Health Organization (WHO) histological classification in comparison with WBPET. MethodsA total of 938 patients with breast cancer underwent WBPET and ring-type DbPET, and 1021 lesions were histologically assessed based on the WHO classification of tumors of the breast. The findings of WBPET and DbPET were retrospectively evaluated and compared. ResultsThe size-related sensitivity of DbPET was superior to that of WBPET for subcentimetric tumors (81.9% vs. 52.4%, P < 0.001). The histological distribution was as follows: 11 lobular carcinoma in situ, 158 ductal carcinoma in situ, 738 infiltrating duct carcinoma not otherwise specified (NOS), 12 lobular carcinoma NOS, 40 mucinous adenocarcinoma, 13 tubular carcinoma, 36 invasive breast carcinoma others, and 13 papillary neoplasms. WBPET had low sensitivity for lobular carcinoma in situ, ductal carcinoma in situ, lobular carcinoma NOS, mucinous adenocarcinoma, and tubular carcinoma. DbPET showed improved sensitivity for all the above except lobular and tubular carcinoma. The maximum standardized uptake values (SUVmax) of DbPET were significantly higher than those of WBPET for histological types, excluding lobular carcinoma in situ. The SUVmax of papillary neoplasms was high regardless of low-grade histology and Ki-67 labeling index. ConclusionsDBPET was found to have high sensitivity and SUVmax values for all histologic types that showed low sensitivity of detection on WBPET, except lobular carcinoma in situ.

The 2020 WHO Classification of Tumors of Bone: An Updated Review.

Bone tumors are a rare and heterogeneous group of neoplasms that occur in the bone. The diversity and considerable morphologic overlap of bone tumors with other mesenchymal and nonmesenchymal bone lesions can complicate diagnosis. Accurate histologic diagnosis is crucial for appropriate management and prognostication. Since the publication of the fourth edition of the World Health Organization (WHO) classification of tumors of soft tissue and bone in 2013, significant advances have been made in our understanding of bone tumor molecular biology, classification, prognostication, and treatment. Detection of tumor-specific molecular alterations can facilitate the accurate diagnosis of histologically challenging cases. The fifth edition of the 2020 WHO classification of tumors of soft tissue and bone tumors provides an updated classification scheme and essential diagnostic criteria for bone tumors. Herein, we summarize these updates, focusing on major changes in each category of bone tumor, the newly described tumor entities and subtypes of existing tumor types, and newly described molecular and genetic data.

Update on pituitary adenomas in the 2017 World Health Organization classification: innovations and perspectives.

The World Health Organization (WHO) classifications of tumors offer invaluable support in the diagnosis of tumors, with every new edition including novel information and diagnostic updates. The new 2017 WHO Classification of Tumors of Endocrine Organs, 4th edition, includes innovations in both terminology and diagnostic guidelines for pituitary adenomas, along with new entities, molecular information, and novel treatment modalities. The recommended reporting system of pituitary adenomas is based on morphology and assessment of the hormonal content by immunohistochemistry. Electron microscopy and immunohistochemistry for Ki-67 and p53 and transcription factors, while presenting additional information, are not recommended for routine diagnosis. Other markers may also yield information of prognostic and predictive significance. In sum, the 2017 WHO classification provides pathologists and clinicians with new and comprehensive information of great use for the diagnosis and treatment of pituitary tumors.