Ace your courses and the USMLE with the go-to review guide-complete with critical concepts and fully updated practice questions Histology and Cell Biology is designed and formatted in a way that helps you make the most of your time, whether you're studying this topic for the first time or reviewing for the USMLE. With this focused review you'll be able to pinpoint your weak areas, then improve your comprehension with learning aids designed to help you understand and retain even the most difficult material. This popular LANGE guide provides everything you need to know about the four basic tissues types, and organs and organ systems. Each chapter is devoted to a specific topic and includes learning aids, such as objectives highlighting significant facts and concepts; study questions directing students to facts commonly covered on exams; synopsis presented in outline form that reviews all the basic histology and related cell biology covered on exams; and multiple-choice practice questions written in USMLE format. This authoritative resource concludes with a diagnostic final exam, updated with longer, case-related stems that mimic the USMLE Step 1 exam. NEW: Thoroughly revised Q&A NEW: Completely updated text and practice questions to reflect current knowledge NEW: Information added to each chapter regarding relevant pathology/clinical issues Good Text for first year students, help understand and piece together professors' lectures Great Practice Q&A

The adipokines (also called adipocytokines), are a group of peptides secreted by adipose tissue. They have diverse roles, from the cell to the whole body. The book is designed for health scientists, doctors, physiologists, immunologists, biochemists, college and university teachers and lecturers, undergraduates and graduates. The chapters are written either by experts or specialists in their field.

The natural killer NK] cell plays a critical role in regulating the innate and adaptive immune response to pathogens, injury and stress. It has emerged as a cell capable of helper function, expansion, contraction, and accelerated memory responses - features similar to other adaptive immune cells. It is a professional accelerator of immunity, mediating dendritic cell maturation and its precursors critical for the origin and development of secondary lymph node structures. These characteristics place the NK cell in a unique position, with a major role in sculpting the host response to damage and injury. This volume is the first complete and authoritative reference to explore these emergent, exciting aspects of the NK cell, placing it at the center of damage/danger recognition and the response to stress. "Natural Killer Cells" details NK cell biology, the role of NK cells in regulating immunity through interactions with other cells and tissues, the participation of NK cells in disease and special topics in NK biology.

- Provides a broad, detailed coverage of the biology and interactions of NK cells for students, fellows, scientists, and practitioners - Includes figures, histologic sections, and illustrations of the ontogeny of NK cells - Companion website includes full-color image database

Perfect for reinforcing knowledge in any level histology course, Netter's Histology Cut-Out Flash Cards, 2nd Edition, offer a convenient and portable histology review - including gross anatomy and histopathology for today's integrated courses and even more clinical relevance. User-friendly and engaging to use, these 200 superbly illustrated cards increase your understanding of important structures and reinforce your understanding of how the human body works in health as well as illness and injury. Printed deck includes perforated guides for cutting each page into four cards: image on front, answers and concise text on back. Prepunched holes are perfect for looping on a ring or keychain for study anytime, anywhere. Microscopic features of cells, tissues, and organs are clearly depicted with classic Netter anatomy illustrations and extensive additional images including histology slides and light and electron micrographs. More basic principles, clinical correlations, and histopathology content prepares you for commonly tested topics on board exams. Master the histology knowledge you need to know by using these flash cards in conjunction with Netter's Essential Histology, 3rd Edition, also by Drs. Ovalle and Nahirney. The cards are cross referenced to the text, making it easy to find more in-depth information on any topic. Enhanced eBook version included with purchase. Your enhanced eBook allows you to access all of the text, figures, and references from the book on a variety of devices.

This book explores several subtypes of muscarinic receptors that modulate smooth muscle activity. Main topics include a classification of muscarinic receptors, biochemical responses that occur in smooth muscle, the role of muscarinic receptors in the function of gastrointestinal and genitourinary smooth muscle, and prejunctional muscarinic receptors in smooth muscle. Discussions cover the current state of research and are intended to generate further research into the design of novel therapeutics for disorders of smooth muscle function.

The second edition of Comparative Anatomy and Histology is aimed at the new rodent investigator as well as medical and veterinary pathologists who need to expand their knowledge base into comparative anatomy and histology. It guides the reader through normal mouse and rat anatomy and histology using direct comparison to the human. The side by side comparison of mouse, rat, and human tissues highlight the unique biology of the rodents, which has great impact on the validation of rodent models of human disease.

The realization that epithelial tissues are not simply passive barriers to the adsorption of materials into internal environments has brought about an enormous growth of investigation of mucosal functions and their active and passive protective roles. Epithelia are highly organized but complex structures, subserving numerous functions, including immunological defence. The use of pharmacological tools in these systems is increasing, which is improving our understanding of epithelial immunobiology.;This volume adopts a step-by-step approach whereby each chapter builds upon the previous one, progressively adding important foundation information, culminating in a series of chapters concerning particular epithelia, including respiratory, gastrointestinal, renal and ocular. The result is a comprehensive, but integrated, treatise of piethelial function and its immunopharmacology, which aims to scrve as an appropriate starting point at which the clinical pulmonologist and the research scientist can obtain an appreciation of some aspects of epithelial immununopharmacology as they are currently understood.

Connective tissue is a multicomponent, polyfunctional complex of cells and extracellular matrix that serves as a framework for all organs, combining to form a unified organism. It is a structure responsible for numerous vital functions such as tissue-organ integration, morphogenesis, homeostasis maintenance, biomechanical support, and more. The regeneration potential of connective tissue affects healing of damaged tissue and organs, while trauma, stress, and other factors that cause damage to connective tissue can lead to numerous disorders. Connective Tissue: Histophysiology, Biochemistry, Molecular Biology brings together crucial knowledge of mammalian connective tissue (including human) and its components, both cellular and noncellular, in one authoritative reference. The breadth and depth of information has fundamental scientific significance as well as applied relevance in clinical medicine. The first half of the book covers the structure, classification, biochemical aspects, histogenesis, and cellular elements of connective tissue. It presents data from the macro- to nanolevel organization of the extracellular matrix-its structural and functional aspects-and addresses metabolic functions and the biochemistry and molecular biology of connective tissue ageing. The second half of the book reviews current data on the biochemistry and molecular biology of skeletal connective tissue, including bone and cartilage metabolism and regulation. It presents an in-depth analysis of data on the molecular mechanisms of connective tissue ontogenesis, from embryonic development through ageing. It also reports novel findings on bone marrow stroma and describes electron microscopy results of the nanostructure of bone mineral, mineralized cartilage, and teeth compared with coral and seashells. Comprising both classic and modern data on the histopathology, biochemistry, and molecular biology of connective tissue, this book provides a unique resource for clinicians and researchers alike.

The endothelium is an excellent example of where biology meets physics and engineering. It must convert mechanical forces into chemical signals to maintain homeostasis. It also controls the immune response, drug delivery through the vasculature, and cancer metastasis. Basic understanding of these processes is starting to emerge and the knowledge gained from research is now being used in applications from drug delivery to imaging modalities. This book reviews current knowledge in mechanobiology of the endothelium and its implications for the development of theranostic devices.

Histology is the discipline of biology that involves the microscopic examination of thin stained tissue sections in order to study their structure and correlate it with function. Histology can detect signs of disease not easily recognized on gross examination and can therefore be of interest in fish health supervision. The aim of this volume is to present a general reference guide providing an extensive set of histological images of fishes (about 40 species). This atlas is designed for use by students and researchers, biologists, ichthyologists, fish farmers, veterinarians working in fisheries and, of course, by comparative histologists who want to learn more about the fish world.

Combining a complete histology atlas with a concise, clinically oriented text, Histology from a Clinical Perspective, 2nd Edition, integrates essential basic science information and related pathology to ensure mastery of fundamental histology topics and the confidence to apply concepts effectively in practice. Explanatory text in each chapter is paired with expanded figure legends in an innovative layout that presents light and electron micrographic images of a tissue, a diagrammatic representation of the same tissue, and an example of how the tissue may be modified by a pathologic process in abundant Clinical Correlations. Rich with clinical vignette USMEL-style review questions and additional self-assessment resources, this student-friendly approach reflects the most up-to-date clinical perspectives and instills the understanding and skills to excel in today's clinical settings. New clinical-vignette USMLE-style questions prepare students for course and board exams. New From Histology to Pathology feature clarifies the impact of pathologic conditions on basic tissue structure with side-by-side comparisons. Detailed labels on the more than 1,300 illustrations and micrographs help you identify structures at a glance. Key Concepts sections and Chapter Summary tables streamline learning with quick access to essential chapter and section takeaways. More than 100 Clinical Correlations accompany examination of normal tissues and structures and visually reinforce relevant pathology. Additional digital feature: Flash cards deliver engaging, interactive review of key structures and characteristics of cells, tissues, and organs.

Now in its second edition, this book remains a vital reference manual for those pathologists whose work involves them in the interpretation of endometrial biopsies. A full account is given of the appearances of the endometrium during the menstrual cycle, of the effects of hormones, the changes induced by steroid contraceptives and intrauterine devices, of functional disorders and of inflammatory disease. Particular attention is given to the various forms of hyperplasia and neoplasia, with special emphasis being placed upon the differential diagnosis of these conditions. Other chapters deal with sampling techniques, the anatomy and histology of the normal endometrium, descriptions of the tissue in normal and abnormal pregnancy, and gestational trophoblastic disease. This fully revised second edition reflects the fact that numerous new entities have been defined, the classification of many disease states has altered and new understanding of many endometrial diseases has been gained. This edition also discusses the changing pattern of endometrial biopsies resulting from modified clinical practice. Biopsy Pathology of the Endometrium provides the pathologist and gynaecologist with a highly illustrated and practical manual whose high quality photomicrographs will be an indispensable reference during the interpretation of endometrial biopsies.

Histopathology: Methods and Protocols provides a comprehensive guide to the current issues in histopathology. With chapters on organ-based approaches with specific protocols for morphologic, molecular examination and pathological observations governing the therapeutic management of the diseases. Written in the highly successful Methods in Molecular Biology series format, chapters include introductions to their respective topics, lists of the necessary materials and reagents, step-by-step, readily reproducible laboratory protocols and tips on troubleshooting and avoiding known pitfalls. Authoritative and practical, Histopathology: Methods and Protocols seeks to be a useful reference for pathologists, pathology residents and fellows as well as to the clinicians and scientists.

This textbook describes the biomechanics of bone, cartilage, tendons and ligaments. It is rigorous in its approach to the mechanical properties of the skeleton yet it does not neglect the biological properties of skeletal tissue or require mathematics beyond calculus. Time is taken to introduce basic mechanical and biological concepts, and the approaches used for some of the engineering analyses are purposefully limited. The book is an effective bridge between engineering, veterinary, biological and medical disciplines and will be welcomed by students and researchers in biomechanics, orthopedics, physical anthropology, zoology and veterinary science. This book also: Maximizes reader insights into the mechanical properties of bone, fatigue and fracture resistance of bone and mechanical adaptability of the skeleton Illustrates synovial joint mechanics and mechanical properties of ligaments and tendons in an easy-to-understand way Provides exercises at the end of each chapter

"Tissue Morphogenesis: Methods and Protocols "highlights major techniques, both experimental and computational, for the study of tissue morphogenesis, divided into several sections, with specific focus on techniques to image, manipulate, model and analyze tissue morphogenesis. Chapters focus on imagining analysis of tissue morphogenesis, culture models of tissue morphogenesis, manipulating cells and tissues in vivo, novel model systems to investigate issue morphogenesis and computational models. Written in the highly successful "Methods in Molecular Biology "series format, chapters include introductions to their respective topics, lists of the necessary materials and reagents, step-by-step, readily reproducible laboratory protocols and tips on troubleshooting and avoiding known pitfalls.

Authoritative and practical," ""Tissue Morphogenesis: Methods and Protocols" serves as a primary resource for both fundamental and practical understanding of the techniques used to uncover the basis of tissue morphogenesis.

Combiningtwodifferentscienti?cdisciplines-morphologyandimmunochemistry- immunohistochemistryhasdevelopedasanimportantinstrumentinresearchand clinicalpathology. A basicunderstandingofunderlying principlesandpotential problemsisunavoidableifyouwanttobesuccessfulinyouruseofimmunohis- chemistry,aswellasingettingyourpaperspublishedandyourresearchgrants funded. Whilemanyexcellenttextsandmonographsexistwhichcovervariousaspects ofimmunohistochemistry,thelackofaconcisecomprehensiveguidetousing thesemethodswasamajormotivationforwritingthisbook. Ourintentionwasto createaneasy-to-readandfocusedresourcebasedonstate-of-the-artinformation forabroadaudiencerangingfromstudentsandtechnicalassistantstoexperienced researchers. Thishandbookhasaconciseformat,withprotocolsandinstructionsfor methodsimmediatelyfollowingtheshortintroductorytheoreticalmaterialineach chapter. BeingconsciousofthegrowingroleofInternetasaninformationsource, wehavefounditreasonableinmanycasestosubstitutecitingbooksandjournal publications with corresponding Internet websites. Where possible, commercial sourcesofreagents,kits,andequipmentarelistedthroughoutthetextinsteadof inaseparateindex. Thougheachchapterissmallandintroductory,thishandbook itself is self-suf?cient and provides a comprehensive look at the principles of immunohistochemistry. For readers wanting further depth of knowledge, each chapterisbackedupbyashortlistofcarefullyselectedoriginalarticles. Duringthelastdecade,pioneeringeffortsofhistochemistshaveledtoan- menseimprovementinthereagentsandprotocols. Theresearcherisurgedalwaysto determinethereasonforeverymethodandstepbeforedoingit. Thishandbookis intendedtohelpreaderstoavoidtroublesinthechoiceofanadequatemethod,which happenswhenusingstandardtextbooks. Forthishandbook,wecarefullyselected establishedmethodsandeasy-to-adoptprotocols,payingattentiontomoderndev- opmentsinimmunohistochemistry,suchasantigenretrieval,signalampli?cation, the use of epitope tags in immunohistochemistry, multiple immunolabeling or diagnosticimmunohistochemistry. Eachofthemethodsdescribedinthishandbook v vi Preface was provedby the authors; many of these methods are routinely used in daily practiceintheirinstitute. Allthepracticalmethodsadvocatedareclearlydescribed, withaccompanyingtables,andtheresultsobtainableareillustratedwithcolour micrographs. Acknowledgements We thank Vera Samoilova forthe perfect technical assistance and other colleaguesfromtheMunsterUniversityClinicforsharingprobesandreagents. IgorB. BuchwalowandWernerBocker Munster Contents 1 AntibodiesforImmunohistochemistry ...1 1. 1 StructureofAntibodies ...2 1. 2 PolyclonalAntibodies ...4 1. 3 MouseMonoclonalAntibodies ...4 1. 4 RabbitMonoclonalAntibodies ...5 1. 5 ProteinAandProteinGinImmunohistochemistry ...7 References ...8 2 AntibodyLabelingandtheChoiceoftheLabel ...9 2. 1 CovalentLabelingofAntibodies ...9 2. 2 Non-CovalentLabelingofPrimaryAntibodieswith LabeledFabFragments ...10 2. 3 EnzymeLabelsforLightMicroscopy ...13 2. 4 FluorophoreLabelsforFluorescenceMicroscopy ...15 2. 5 ColloidalGoldLabelsforElectronMicroscopy ...16 References ...17 3 ProbesProcessinginImmunohistochemistry ...19 3. 1 FixationinImmunohistochemistry ...19 3. 1. 1 FixationinAlcoholsandAcetone ...20 3. 1. 2 FixationinFormaldehyde ...20 3. 1. 3 EffectofFormaldehydeFixationon Antigen-nster Contents 1 AntibodiesforImmunohistochemistry ...1 1. 1 StructureofAntibodies ...2 1. 2 PolyclonalAntibodies ...4 1. 3 MouseMonoclonalAntibodies ...4 1. 4 RabbitMonoclonalAntibodies ...5 1. 5 ProteinAandProteinGinImmunohistochemistry ...7 References ...8 2 AntibodyLabelingandtheChoiceoftheLabel ...9 2. 1 CovalentLabelingofAntibodies ...9 2. 2 Non-CovalentLabelingofPrimaryAntibodieswith LabeledFabFragments ...10 2. 3 EnzymeLabelsforLightMicroscopy ...13 2. 4 FluorophoreLabelsforFluorescenceMicroscopy ...15 2. 5 ColloidalGoldLabelsforElectronMicroscopy ...16 References ...17 3 ProbesProcessinginImmunohistochemistry ...19 3. 1 FixationinImmunohistochemistry ...19 3. 1. 1 FixationinAlcoholsandAcetone ...20 3. 1. 2 FixationinFormaldehyde ...20 3. 1. 3 EffectofFormaldehydeFixationon Antigen- immunohistochemistryhasdevelopedasanimportantinstrumentinresearchand clinicalpathology. A basicunderstandingofunderlying principlesandpotential problemsisunavoidableifyouwanttobesuccessfulinyouruseofimmunohis- chemistry,aswellasingettingyourpaperspublishedandyourresearchgrants funded. Whilemanyexcellenttextsandmonographsexistwhichcovervariousaspects ofimmunohistochemistry,thelackofaconcisecomprehensiveguidetousing thesemethodswasamajormotivationforwritingthisbook. Ourintentionwasto createaneasy-to-readandfocusedresourcebasedonstate-of-the-artinformation forabroadaudiencerangingfromstudentsandtechnicalassistantstoexperienced researchers. Thishandbookhasaconciseformat,withprotocolsandinstructionsfor methodsimmediatelyfollowingtheshortintroductorytheoreticalmaterialineach chapter. BeingconsciousofthegrowingroleofInternetasaninformationsource, wehavefounditreasonableinmanycasestosubstitutecitingbooksandjournal publications with corresponding Internet websites. Where possible, commercial sourcesofreagents,kits,andequipmentarelistedthroughoutthetextinsteadof inaseparateindex. Thougheachchapterissmallandintroductory,thishandbook itself is self-suf?cient and provides a comprehensive look at the principles of immunohistochemistry. For readers wanting further depth of knowledge, each chapterisbackedupbyashortlistofcarefullyselectedoriginalarticles. Duringthelastdecade,pioneeringeffortsofhistochemistshaveledtoan- menseimprovementinthereagentsandprotocols. Theresearcherisurgedalwaysto determinethereasonforeverymethodandstepbeforedoingit. Thishandbookis intendedtohelpreaderstoavoidtroublesinthechoiceofanadequatemethod,which happenswhenusingstandardtextbooks. Forthishandbook,wecarefullyselected establishedmethodsandeasy-to-adoptprotocols,payingattentiontomoderndev- opmentsinimmunohistochemistry,suchasantigenretrieval,signalampli?cation, the use of epitope tags in immunohistochemistry, multiple immunolabeling or diagnosticimmunohistochemistry. Eachofthemethodsdescribedinthishandbook v vi Preface was provedby the authors; many of these methods are routinely used in daily practiceintheirinstitute. Allthepracticalmethodsadvocatedareclearlydescribed, withaccompanyingtables,andtheresultsobtainableareillustratedwithcolour micrographs. Acknowledgements We thank Vera Samoilova forthe perfect technical assistance and other colleaguesfromtheMunsterUniversityClinicforsharingprobesandreagents. IgorB. BuchwalowandWernerBocker Munster Contents 1 AntibodiesforImmunohistochemistry ...1 1. 1 StructureofAntibodies ...2 1. 2 PolyclonalAntibodies ...4 1. 3 MouseMonoclonalAntibodies ...4 1. 4 RabbitMonoclonalAntibodies ...5 1. 5 ProteinAandProteinGinImmunohistochemistry ...7 References ...8 2 AntibodyLabelingandtheChoiceoftheLabel ...9 2. 1 CovalentLabelingofAntibodies ...9 2. 2 Non-CovalentLabelingofPrimaryAntibodieswith LabeledFabFragments ...10 2. 3 EnzymeLabelsforLightMicroscopy ...13 2. 4 FluorophoreLabelsforFluorescenceMicroscopy ...15 2. 5 ColloidalGoldLabelsforElectronMicroscopy ...16 References ...17 3 ProbesProcessinginImmunohistochemistry ...19 3. 1 FixationinImmunohistochemistry ...19 3. 1. 1 FixationinAlcoholsandAcetone ...20 3. 1. 2 FixationinFormaldehyde ...20 3. 1. 3 EffectofFormaldehydeFixationon Antigen-AntibodyBinding ...21 3. 2 Paraf?nSectionsforImmunohistochemicalAnalysis ...22 3. 2. 1 EmbeddingandCutting ...22 3. 2. 2 MountingParaf?nSectionsontoSlides ...23 3. 3 CryosectionsforImmunohistochemicalAnalysis ...24 3. 4 BuffersforWashingandAntibodyDilution ...25 3. 5 MountingFollowingImmunohistochemicalStaining ...27 3. 6 StorageFollowingImmunohistochemicalStaining ...28 References ...28 vii viii Contents 4 WorkingwithAntibodies ...31 4. 1 DirectImmunostainingMethod ...31 4. 2 IndirectImmunostainingMethod ...33 4. 3 TheChoiceofAntibodies ...35 4. 3. 1 TheChoiceofPrimaryAntibodies ...35 4. 3. 2 TheChoiceofSecondaryAntibodies ...

This classification represents a project aimed at bringing together the variety of ways thymic epithelial neoplasms have been classified. It focuses on their growth characteristics, and cytoarchitectural features . The classification, though restricted to the thymic region rather than the mediastinum in general, also covers neuroendocrine, germ cell, lymphoid, and stromal tumours, as well as tumour-like lesions and the neck tumours of thymic or related branchial pouch derivation.

The 1973 WHO classification of bladder tumours anticipated a probable need for eventual revision of the criteria for diagnosing papillary and flat bladder neoplasia. A workshop sponsored by the WHO consisting of pathologists, urologists, cytologists, oncologists and basic scientists interested in bladder tumours addressed this subject, and after a follow- -up meeting sponsored by the International Society of Urological Pathology, the classification and terminology used in this text were agreed upon. A major change is in the introduction of a new category: papillary urothelial neoplasm of low malignant potential. Many of the tumours previously designated as papillary transitional cell carcinoma, grade I now fall into that category. Another major change is in the designation of flat lesions, and this includes a definition of carcinoma in situ. Furthermore, a number of variant forms of urothelials carcinomas are included as well as new entities not recognized when the 1st edition was issued.

This book differs from others in the Histological Typing series by including more clinical aspects and by concentrating on cancer and precancer of the oral mucosa rather than attempting to cover all benign and malignant tumors of the oral and oropharyngeal tissue. One main aim is to inform general pathologists of the significance of the clinical features of the various lesions discussed as, on the whole, they may be unfamiliar with this territory. Attention is also drawn to those conditions particular to the oral mucosa that may give rise to appearances which are important in differential diagnoses but can be misleading to the pathologist who does not have detailed knowledge of the tissue involved. The TNM-classification for malignant tumors of the lip and oral cavity is also included.

This is a classification of tumours and tumour-like lesions of the liver. It is based primarily on the microscopic characteristics of the tumours, and is therefore concerned with morphologically identi- fiable cell types and histological patterns. The haematoxylin- and eosin-stained section remains the mainstay of morphological diag- nosis, but special histochemical stains are often helpful and have been referred to in the explanatory notes. Readers interested in specific special stains mentioned in the text should consult Labora- tory Methods in Histotechnology of the Armed Forces Institute of *Pathology, Washington, D. c., USA. 1 The results of immunohisto- chemical methods for identifying various tumour "markers" have also been noted whenever indicated. The present classification incorporates all the previously classi- fied tumours, but also includes several new lesions, viz. biliary papil- lomatosis, the fibrolamellar variant of hepatocellular carcinoma and epithelioid haemangioendothelioma. Several subtypes of hepato- blastoma are mentioned. A serous type of bile duct cystadenoma is described. The section on tumour-like lesions has been expanded to include focal fatty change and inflammatory pseudotumour. The section on adenomatous hyperplasia, including macroregenerative nodules, has been amplified. The number of photomicrographs has been increased from the original 56 to 150. Unlike the first edition, the photomicrographs in the second edition are mostly black and white. All are new and were taken of representative cases on file at the Armed Forces Institute of Pathology.

The task of updating the classification was given to the Classification and Nomenclature Committee of the International Society of Gynecological Pathologists and its four subcommittees. This classification reflects the present state of knowledge and modifications are almost certain to be needed as experience accumulates. Since many of the tumours and tumour-like conditions in the classification occur in several sites in the female genital tract, cross-referencing from one site to another has been done in illustrating these lesions.

During the two decades since the publication of the first edition of Histological Typing of Bone Tumours, new methods of diagnosis, es- pecially radiological imaging techniques (computed tomography and magnetic resonance imaging), associated with advances in the new cytomorphological methods including immunohistochemistry, DNA ploidy analysis, cytogenetic chromosomal investigation, etc., have greatly improved our diagnostic tools and treatment results. These advances are reflected by the publication of new editions of various important textbooks in recent years. In these publications classifica- tion criteria differed. In contrast, the WHO classification has been relatively unaltered, and has introduced a limited number of new entities and subdivided others because of distinct histological features and biological be- haviour. In general the framework and the concept of the original classifi- cation, as it has been widely accepted, remains essentially unchanged. The classification is based on the line of histological differentiation, in many instances reflecting the type of intercellular matrix material produced. This approach is justified because it avoids theoretical his- togenetic controversies.

Knowledge of tumours of the thyroid gland has advanced consider- ably in the 22 years that have elapsed since work was started on the first edition of Histological Typing of Thyroid Tumours. In the intro- duction to that volume it was recognized that the definitions and clas- sifications put forward would need revision in time, and the present text differs substantially from the first edition. As far as is possible, however, the framework of the classification proposed remains the same, as the original classification was widely accepted and proved useful in many studies. The link between the morphological type of thyroid tumour and its epidemiology, natural history, function, prognosis and response to therapy has been further strengthened since the first edition. In par- ticular, the decision taken to separate papillary and follicular carcino- mas and exclude a mixed papillary follicular type has been well justi- fied. One of the major changes has been the recognition that many tu- mours regarded 20 years ago as small cell carcinoma were really ma- lignant lymphoma, and this development has been incorporated into this edition, with increased importance given to primary malignant lymphoma of the thyroid. Much work has also been done on medul- lary carcinoma of the thyroid, its link with mUltiple endocrine neo- plasia syndromes, and its association in its inherited form with C-cell hyperplasia; this too is recognized by an expanded section on this tu- mour.

Although more than 12 years have passed since publication of the first WHO histological classification of central nervous system (CNS) tumours, the changes in this revised edition are not radical. Only one formerly recognized entity has been deleted: the monstrocellular sarcoma, because there is immuno- cytochemical evidence of its astrocytic nature. Several new tumour types have been added: the pleomorphic xanthoastro- cytoma has been generally acknowledged for almost a decade; the neurocytoma has gradually evolved as a clinical-pathological entity; and two new entries, the dysembryoplastic neuroepi- thelial tumour and the desmoplastic infantile ganglioglioma, have only been characterized morphologically during the past few years. We regard the classification as an international standard to facilitate communication and have tried to avoid current con- ceptual controversies. The majority of partiCipants supported inclusion of the term "primitive neuroectodermal tumour" (pNET). However, because of our limited knowledge of the biol- ogy of embryonal CNS tumours, preference was given to use PNET selectively, rather than applying it to all small cell embryo- nal childhood tumours, irrespective of their histological pheno- type. Ependymomas and meningiomas now have new histological SUbtypes. Most of these are not associated with biological behaviour different from the parent tumour type, but their description will aid the practising pathologist to identify and classify these lesions. 2 Introduction Histological Typing Following the philosophy of this WHO series, classification is based primarily on histological assessment of cell types and tis- sue patterns recognized by conventional light microscopy.

1. 1 The Cytokeratins as a Member of the Intermediate Filament Protein Family Intermediate filaments together with microtubules and actin microfilaments make up the filamentous cytoskeleton found in the cytoplasm of vertebrate cells. Recently, intermediate filament proteins have also been described in invertebrates, but their chemistry is not yet known (for review see Biessmann and Walter 1989). These filaments (about 10 nm in diameter) used to be categorized into five classes - cytokeratin, vimentin, desmin, glial fibrillary acidic protein (GFAP), and neurofilaments (NFs). The expression of these proteins follows differentiation-dependent rules: cytokeratins occur in epi- thelial cells, NF proteins are expressed in neurons, GFAP in astrocytes and some nonglial cells, desmin in smooth muscle cells and in striated myocytes, and vimentin in mesenchymal cells (for review see Lazarides 1980; Osborn and Weber 1983). Recent investigations including deoxyribonucleic acid (DNA) and protein sequencing and peptide mapping have redefined the intermediate filaments into five types or subfamilies (type I, acidic cytokeratins; type II, basic cytokeratins; type III, vimentin, desmin, peripherin, and GFAP; type IV, the three NF proteins; and type V, the nuclear lamins (for review see Nagle 1988). A new type VI intermediate filament protein, nestin, has been described in the developing nervous system (Lendahl et al. 1990), and is initially co- expressed with vimentin in neuroepithelial stem cells (Steinert and Liem 1990). The cytokeratins are the most complex subgroup of intermediate filament proteins.