Introduction to Pathology Lecture 1 PDF

INTRODUCTION OF PATHOLOGY INTRODUCTION TO PATHOLOGY  Learning Objectives Upon completing this chapter students should be able to: 1. Define pathology 2. Discuss the core aspects of disease in pathology 3. Know the diagnostic techniques used in pathology 4. Know the various categories of the causes...

INTRODUCTION OF PATHOLOGY INTRODUCTION TO PATHOLOGY  Learning Objectives Upon completing this chapter students should be able to: 1. Define pathology 2. Discuss the core aspects of disease in pathology 3. Know the diagnostic techniques used in pathology 4. Know the various categories of the causes of diseases 5. Know the course, outcome, consequences of diseases PATHOLOGY  The word Pathology’ is derived from two Greek words—  pathos (meaning suffering)  logos (meaning study).  Pathology is, thus, scientific study of changes in the structure and function of the body in disease.  Pathology consists of the abnormalities in normal anatomy (including histology) and normal physiology owing to disease. IMPORTANCE OF STUDY OF PATHOLOGY  General knowledge of how disease are caused.  General patterns and classification of diseases  Evolution of disease from its causes to clinical presentation  The signs and symptoms of disease  Nature, spread and precautions to prevent common diseases  Know the different disciplines that make up pathology  Better understand the patient and his disease. IMPORTANCE OF THE STUDY OF PATHOLOGY FOR NURSES 1. Nurses today are not merely restricted to providing bedside care to sick and injured hospitalized patients; they have more challenging expansions and extensions of their role in health care delivery system. 2. The study of pathology will prepare the nurses to understand how the disease started, what was the main cause of disease process, how diseases are diagnosed and what changes may be expected at cellular, tissue and organ level during the illness. 3. To understand the patterns and classification of diseases Understanding the causes of disease: The knowledge of pathology will equip the nurses with following essential information related to etiology and pathogenesis of diseases IMPORTANCE OF THE STUDY OF PATHOLOGY FOR NURSES 4. To understand the etiology and pathophysiological mechanisms, which underlie a disease process Understanding the basic nature of diseases such as inflammatory, degenerative, hemodynamic, infective, autoimmune and neoplastic 5. Knowledge about Pathology serves as a foundation for nurses to understand the pathophysiology of a disease, so that nursing care can be planned more efficiently 6. To correlate the clinical features with the structural and functional pathological alterations in the organs due to the disease process. IMPORTANCE OF THE STUDY OF PATHOLOGY FOR NURSES 7. To appraise the evolution of disease from its causes to the clinical presentation including signs and symptoms of diseases. 8. To understand the morphological changes, which take place in the body during various disease processes. 9. Progression of the Disease: The knowledge of pathology helps the nurses to understand the basic structural and functional changes that occur in tissues, organs and the body as a whole. Furthermore, knowledge of pathology helps the nurses: DEFINITION OF TERMS  Accession number: A unique case number assigned to each specimen sample to be analyzed.  Actinic: Related to sun-exposure.  Anatomic Pathology: General term for the area of pathology that deals with the gross and microscopic analysis of organs, tissues, and cells, which includes surgical pathology, cytopathology, and autopsy.  Autopsy: Postmortem evaluation of a body to determine the cause and manner of death.  Biopsy: Removal of cells or tissues from the body for pathological examination.  Blocks: Hardened tissues encased in wax blocks that are cut to produce glass microscopic slides.  Carcinoma: A malignant tumor composed of “epithelial” cells, which can be seen in almost any body location. DEFINITION OF TERMS  Clinical Pathology: A group of practice areas in laboratory medicine that is concerned with diagnosing disease based on the analysis of body fluids.  Core Biopsy: A biopsy in which a cylindrical sample of tissue is obtained (as from a kidney or breast) by a hollow needle.  Cyst: A sac or pouch containing fluid or other materials that is encased by a tissue membrane.  Cytogenetics: The study of chromosome-related structures.  Cytology: The study of individual cells with the microscope.  Cytopathology: A subspecialty of anatomic pathology that focuses on the diagnosis of diseased cells in specimens derived from body fluids or aspirated tissue.  Dermatology: The branch of medicine that deals with the skin and diseases affecting the skin DEFINITION OF TERMS  Dermatopathology: The subspecialty of anatomic pathology which deals with skin diseases.  Diagnosis: Identification of a specific disease process by a physician.  Dysplastic: Structurally-abnormal.  Effusion: An abnormal collection of fluid in one or more of the body spaces.  Ellipse: An almond-shaped portion of surgically-removed skin, usually with an abnormal area in its center.  Examination (of tissue): The process of analysis, identification, evaluation, interpretation, and review of specifically prepared slides by a pathologist.  Excision: Surgical removal of tissue with a scalpel.  Exfoliative Cytology: The microscopic analysis of cells that are shed into body cavities.  Fine Needle Aspiration (FNA): An alternative procedure to formal surgery for obtaining biopsies, in which cells are removed by drawing them under vacuum pressure through a fine needle. DEFINITION OF TERMS  Flow Cytometry: Analysis of cells in fluid samples using special light sources and detectors.  Fluorescent In Situ Hybridization (FISH): A special cytogenetic procedure in molecular pathology to identify specific nucleic acid sequences in cellular nuclei.  Gastrointestinal (GI) & Liver Pathology: Subspecialties in anatomic pathology that focus on diseases in the digestive tract and liver.  Gross Description: An examination based on a description of material that is visible to the naked eye.  Gynecological Pathology: A subspecialty area of anatomic pathology that focuses on diseases of the female genital tract (breast, uterus, fallopian tubes, ovaries, vagina, and vulva).  H&E: An abbreviation for hematoxylin and eosin stains, common biological dyes that give tissue elements distinct colors. These are most often pink, blue, red, and purple.  Hematopathology: A subspecialty area of clinical pathology involving the study of diseases of the blood cells, bone marrow, spleen, and lymph nodes. DEFINITION OF TERMS  Histology: A branch of anatomy that deals with the minute structure of animal and plant tissues as discernible with the microscope  Immunohistochemistry: A microscopic method for localizing specific proteins in tissues through the use of antibodies that are labeled with biological dyes.  Inflammatory: A term concerning diseases that are caused by white blood cells which abnormally enter various tissues.  Keratosis: A benign growth of cells on the skin surface.  Lesion: An abnormality in tissue that is seen with the naked eye or in x-ray studies, or felt by the patient or a physician.  Leukemia: A malignant proliferation of white blood cells that originate in the bone marrow and circulate in the bloodstream. DEFINITION OF TERMS  Lichenoid: Pertaining to a particular linear arrangement of inflammatory cells under the surface of the skin.  Lumpectomy: A common procedure to remove a mass from a male or female breast.  Lymphoma: A malignant proliferation of lymphocytes, which are cells involved in immune functions.  Macroscopic: An examination based on material that is visible to the naked eye.  Margins: Cuffs of healthy or normal tissue on either side of a disease (usually a tumor).  Malignant: Tending to become worse and end in death or having the properties of anaplasia, invasiveness, and metastasis; said of tumors.  Mass: A localized swelling in tissue which may or may not represent a tumor (neoplasm; see below).  Mastectomy: Medical term for the partial or complete surgical removal of a breast. DEFINITION OF TERMS  Melanoma: A malignant proliferation of pigment-producing cells in the skin or other organs.  Microscopic: Visible only with a microscope and not with the naked eye.  Microtome: A device with a sharp blade, used in the laboratory for cutting tissues so that they can be affixed to glass slides and examined with a microscope after staining with biological dyes.  Mole: A commonly used term for a growth on the skin, which may or may not contain pigment.  Molecular Pathology: A field in pathology that combines aspects of clinical and anatomic pathology, with a focus on molecular cell components.  Needle Biospy: Any of several methods (as fine needle aspiration or core biopsy) for obtaining a sample of cells or tissue by inserting a hollow needle through the skin and withdrawing the sample from the tissue or organ to be examined DEFINITION OF TERMS  Neoplasm: An independently-growing mass of cells in the skin or elsewhere, which may be benign or malignant. Neoplasms also are commonly called “masses” or “tumors.”  Neuropathology: A subspecialty area of anatomic pathology that concerns diseases of the central nervous system, muscles, and nerves.  Nevus: A growth on the skin, which is often pigmented (colored).  Pap Smear: A screening test procedure named after pathologist George Papanicolaou (1883 – 1962) in which cells from a woman’s cervix (uterus) are examined microscopically for abnormalities.  Pathologist: A doctor who identifies diseases by studying cells and tissues under a microscope.  Pathology: The scientific study of the nature of disease and its causes, processes, development, and consequences.  Pathology Report: A formal document containing the diagnostic findings of a pathologist, pertaining to a particular biopsy specimen. DEFINITION OF TERMS  Pediatric Pathology: A subspecialty area of pathology concentrating on diseases of infants & children.  Polyp: A specific type of abnormal growth on the skin or on mucous membranes, which projects above the surfaces of those tissues.  Prognosis: An informed estimate of the probable course and biological behavior of a disease process.  Psoriasiform: Resembling the clinical or microscopic image of psoriasis.  Renal Pathology: A subspecialty of anatomic pathology with a focus on kidney diseases.  Requisition: A formal request for laboratory services containing relevant information on a particular patient, the specimen type, and the referring physician.  Sarcoma: A malignant proliferation of connective-tissue cells.  Slides: A general term for thin sheets of glass on which tissue specimens are placed for microscopic analysis. DEFINITION OF TERMS  Specimen: A small part of the human body—either tissue or liquid– that serves as a sample for pathologic evaluation.  Spongiotic: A disease in which excess fluid is seen in the surface layer (epidermis) of the skin.  Surgical Pathology: A subspecialty area of anatomic pathology which focuses on the evaluation of any tissue that is removed by surgical means Diseases  Diseases may, in turn, be defined as an abnormal variation in structure or function of any part of the body.  Pathology gives explanations of a disease by studying the following four aspects of the disease. 1. Etiology 2. Pathogenesis 3. Morphologic changes 4. Functional derangements and clinical significance. Etiology  Etiology of a disease means the cause of the disease. If the cause of a disease is known it is called primary etiology. If the cause of the disease is unknown it is called idiopathic.  Knowledge or discovery of the primary cause remains the backbone on which a diagnosis can be made, a disease understood, & a treatment developed.  There are two major classes of etiologic factors: genetic and acquired (infectious, nutritional, chemical, physical, etc). Detailed discussion will be given in subsequent topics. The etiology is followed by pathogenesis. Pathogenesis  Pathogenesis means the mechanism through which the cause operates to produce the pathological and clinical manifestations.  The pathogenetic mechanisms could take place in the latent or incubation period. Pathogenesis leads to morphologic changes. Morphologic changes  The morphologic changes refer to the structural alterations in cells or tissues that occur following the pathogenetic mechanisms.  The structural changes in the organ can be seen with the naked eye or they may only be seen under the microscope.  Those changes that can be seen with the naked eye are called gross morphologic changes & those that are seen under the microscope are called microscopic changes.  Both the gross & the microscopic morphologic changes may only be seen in that disease, i.e. they may be specific to that disease. Functional derangements and clinical significance  The morphologic changes in the organ influence the normal function of the organ.  By doing so, they determine the clinical features (symptoms and signs), course, and prognosis of the disease. Diagnostic techniques used in pathology  The pathologist uses the following techniques to the diagnose diseases: a. Histopathology b. Cytopathology c. Hematopathology d. Immunohistochemistry e. Microbiological examination f. Biochemical examination g. Cytogenetics h. Molecular techniques i. Autopsy Diagnostic techniques used in pathology A. Histopathological techniques  Histopathological examination studies tissues under the microscope.  During this study, the pathologist looks for abnormal structures in the tissue. Tissues for histopathological examination are obtained by biopsy.  Biopsy is a tissue sample from a living person to identify the disease. Biopsy can be either incisional or excisional. Diagnostic techniques used in pathology A. Histopathological techniques  Once the tissue is removed from the patient, it has to be immediately fixed by putting it into adequate amount of 10% Formaldehyde (10% formalin) before sending it to the pathologist.  The purpose of fixation is: 1. to prevent autolysis and bacterial decomposition and putrefaction 2. to coagulate the tissue to prevent loss of easily diffusible substances 3. to fortify the tissue against the deleterious effects of the various stages in the preparation of sections and tissue processing. 4. to leave the tissues in a condition which facilitates differential staining with dyes and other reagents. ❑ The whole purpose of the tissue processing is to prepare a very thin tissue (i.e. five to seven μm or one cell thick tissue) which can be clearly seen under the microscope. Diagnostic techniques used in pathology B. Cytopathologic techniques Cytopathology is the study of cells from various body sites to determine the cause or nature of disease.  Applications of cytopathology: The main applications of cytology include the following: 1. Screening for the early detection of asymptomatic cancer For example, the examination of scrapings from cervix for early detection and prevention of cervical cancer. 2. Diagnosis of symptomatic cancer Cytopathology may be used alone or in conjunction with other modalities to diagnose tumors revealed by physical or radiological examinations. It can be used in the diagnosis of cysts, inflammatory conditions and infections of various organs. 3. Surveillance of patients treated for cancer For some types of cancers, cytology is the most feasible method of surveillance to detect recurrence. The best example is periodic urine cytology to monitor the recurrence of cancer of the urinary tract. Diagnostic techniques used in pathology B. Cytopathologic techniques Cytopathology is the study of cells from various body sites to determine the cause or nature of disease. Advantages of cytologic examination  Compared to histopathologic technique it is cheap, takes less time and needs no anesthesia to take specimens.  Therefore, it is appropriate for developing countries with limited resources like Ghana.  In addition, it is complementary to histopathological examination. Diagnostic techniques used in pathology C. Hematological examination  This is a method by which abnormalities of the cells of the blood and their precursors in the bone marrow are investigated to diagnose the different kinds of anemia & leukemia. D. Immunohistochemistry  This is a method is used to detect a specific antigen in the tissue in order to identify the type of disease. Diagnostic techniques used in pathology E. Microbiological examination  This is a method by which body fluids, excised tissue, etc. are examined by microscopical, cultural and serological techniques to identify micro-organisms responsible for many diseases. F. Biochemical examination  This is a method by which the metabolic disturbances of disease are investigated by assay of various normal and abnormal compounds in the blood, urine, etc. Diagnostic techniques used in pathology G. Clinical genetics (cytogenetics)  This is a method in which inherited chromosomal abnormalities in the germ cells or acquired chromosomal abnormalities in somatic cells are investigated using the techniques of molecular biology. H. Molecular techniques  Different molecular techniques such as fluorescent in situ hybridization, Southern blot, etc... can be used to detect genetic diseases. I. Autopsy  Autopsy is examination of the dead body to identify the cause of death. This can be for forensic or clinical purposes The causes of disease  Diseases can be caused by either environmental factors, genetic factors or a combination of the two. A. Environmental factors  Environmental causes of disease are many and are classified into: 1. Physical agents 2. Chemicals 3. Nutritional deficiencies & excesses 4. Infections & infestations 5. Immunological factors 6. Psychogenic factors The causes of disease  Diseases can be caused by either environmental factors, genetic factors or a combination of the two. B. Genetic Factors  These are hereditary factors that are inherited genetically from parents. Course of disease The course of disease is shown with a simplified diagram as follows.  Exposure  Biological onset  Clinical onset  Permanent damage  Death Course of disease ❑ The course of a disease in the absence of any intervention is called the natural history of the disease. The different stages in the natural history of disease include: a) Exposure to various risk factors (causative agents) b) Latency, period between exposure and biological onset of disease c) Biological onset of disease; this marks the initiation of the disease process, however, without any sign or symptom. Following biological onset of disease, it may remain asymptomatic or subclinical (i.e. without any clinical manifestations), or may lead to overt clinical disease. d) Incubation (induction) period refers to variable period of time without any obvious signs or symptoms from the time of exposure Course of disease ❑ The course of a disease in the absence of any intervention is called the natural history of the disease. The different stages in the natural history of disease include: e) The clinical onset of the disease, when the signs and symptoms of the disease become apparent. The expression of the disease may be variable in severity or in terms of range of manifestations. f) The onset of permanent damage, and g) Death ❑ Natural recovery, i.e. recovery without any intervention, can occur at any stage in the progression of the disease. Outcome and consequences of disease  Following clinical onset, disease may follow any of the following trends: a) Resolution can occur leaving no sequelae b) The disease can settle down, but sequelae are left, or c) It may result in death. Clinical & biologic death Clinical death  Clinical death is the reversible transmission between life and biologic death.  Clinical death is defined as the period of respiratory, circulatory and brain arrest during which initiation of resuscitation can lead to recovery. Clinical & biologic death Biological Death ❑ Biological death (sure sign of death), which sets in after clinical death, is an irreversible state of cellular destruction. ❑ It manifests with irreversible cessation of circulatory and respiratory functions, or irreversible cessation of all functions of the entire brain, including brain stem. However, one should notice that there are internationally accepted criteria to diagnose biological death