Introduction to Pathology PDF

OG THOL Y TEA M PA Introduction to Pathology Color Index: Main text Important Boys slides only...

OG THOL Y TEA M PA Introduction to Pathology Color Index: Main text Important Boys slides only Girls slides only Doctor’s Notes Editing file Extra info OBJECTIVES: Understands the role of pathology and its various subspecialities in the diagnostic process with special emphasis on histopathology and cytology. Understands the meaning of the terminology used during the study of a disease like aetiology, pathogenesis, prognosis, sequelae, symptoms, signs, incidence etc.. Role of diagnostic pathology in disease management. Be aware of some of the principle techniques used in pathology like light microscopy, cytology, immunohistochemistry and molecular pathology. Be aware of some of the principle techniques used in pathology like light microscopy, cytology, immunohistochemistry and molecular pathology. Have a basic knowledge of the definition of autopsy and its indications. Definition Of Pathology Pathology is the study of disease by scientific methods. It is the study of changes which occur in cells and tissues as a result of any injury to the cell or tissue. Disease is defined as an abnormality in structure or function of any part of the body Parts of pathology The following are the 5 major aspects studied as part of pathology of any disease: Epidemiology Clinical features Etiology (signs and symptoms) Parts of pathology Morphological Pathogenesis changes  1-Epidemiology: Study of the occurrence and distribution of diseases in a population and the application of this knowledge to help the health system. It is the study of the patterns, causes, and effects of disease conditions in various populations. Epidemiology studies provide information regarding the following factors : Age. Sex. Race. Occupation : workers in asbestos industry ( ‫ → ) مصانع االسمنت‬can have diseases like asbestosis or tumors like mesotheliomas. workers in aniline dye industry → can have urinary bladder cancer. hardwood workers → can have nasal cancer from inhalation of wood dust. Geographic location : which part of the world a particular disease is common in. underdeveloped countries → has more malnutrition and infections like tuberculosis. developed countries → have more cardiac problems, obesity related diseases etc. Socioeconomic strata : what is the social and financial status of the people affect by a particular disease. Prevalence : is the total number of cases of a particular disease IMPORTANT to know the in a particular population in a particular period of difference : time. Prevalence → TOTAL number of cases Incidence : Incidence → number of NEW cases is the number of new cases of a particular disease in a particular population in a particular period of time (immunization programmes affect the incidence of a disease).  Sequalea : is the complication or the consequence of a disease. Prognosis : is the expected outcome of the disease based on severity of any disease. (to memorize it : Predict of the outcomes ) Morbidity : is the presence of illness. Mortality rate : is a measure of the number of people dead in a particular population during a particular period of time. Mortality rate can be calculated for any particular disease e.g. mortality rates are high for people with high grade cancers. What is the purpose or Importance of epidemiology? To investigate the extent of a disease in a community To study natural pattern/history and prognosis of disease To identify causes and risk factors To provide good health care based on the findings To recommend and assist in various health programmes to prevent or treat disease (preventive and therapeutic measures), e.g. immunizations and screening programs for different disease etc To evaluate all health care facilities and programs To Provide information on public health in order to help the health care system and develop health policies.  2-Etiology & classification of disease: Etiology means the cause of the disease If the cause of the disease is unknown it is called idiopathic/ cryptogenic/ essential etc. Diseases are classified depending on the etiology and pathogenic mechanism involved. Disease can be: congenital acquired Congenital Disease Is a condition existing at birth or before birth, or that develops during the first month of life. It can be: Category Example -Hemophilia -> x chromosome linked disorder -Down syndrome → chromosomal abnormality with extra Genetic /chromosomal chromosome 21 -Inborn error of metabolism Non-genetic: Birth defect: An Abnormal defect or -Cleft lip deformity a child is born -Spina bifida with.  Acquired Diseases They can be: Category Example Inflammatory -Rhematoid arthritis -Bacterial Infective -Viral -Fungal Vascular -Atherosclerosis (heart attack) Immune mediated —Vasculitis -Alzheimer’s Degenerative -Parkinsonism Neoplastic (Growth disorder) Cancer -Certain drugs can cause liver or kidney failure, bone marrow Therapeutic or recreational suppression, skin rash. drug associated disease -Alcohol can cause liver diseas, paraquat poisoning damages the lungs and excessive smoking causes lung and cardiac problems -Gout Metabolic -Diabetes mellitus Nutritional deficiency -Anemia diseases -Protein energy malnutrition -Radiation to neck can cause thyroid cancer Radiation -Radiation to skin causes skin cancer (squamous cell carcinoma) -Road traffic accident Mechanical -Burns  3-Pathogenesis: it is the steps that take place in the body once the problem begins (whatever it may be) that finally lead to tissue injury (pathological manifestations). Degenerative Immunological process process The four basic pathogenetic mechanisms (or steps that usually take place in diseases) Inflammatory Carcinogenesis process transformation of normal cells to malignant Pathogenesis leads to morphologic changes (changes in the gross or microscopic appearance of human tissue)  4-Morphologic changes: The morphologic changes are the structural changes that take place in cells or tissues due to any disease These morphological changes can be seen as : Grossly (called macroscopic findings) with the naked eye sometimes they can only be seen under the light microscope (called microscopic/histologic findings) Commonly diseases have certain specific gross or microscopic changes and this helps in the diagnosis of that disease 5-Clinical features (functional alterations): When an organ is damaged by a disease, the normal function of that organ is affected and this will lead to the development certain clinical changes called signs & symptoms. The combination of signs and symptoms is called clinical features Symptoms is something experienced and reported by the patient ( e.g. ‘I am feeling tired’, ‘I have a headache’, ‘I have a pain in my stomach’ ) Basically it is what the patient will tell the doctor. Signs are findings discovered by the physician during examination of the patient ( e.g. doctor finds a swelling somewhere or doctor find a liver or spleen enlargement while examining the abdomen ) Basically it is what the doctor will find on examining the patient. THEREFORE IN MEDICINE, DISEASES ARE STUDIED UNDER THE FOLLOWING HEADINGS: Definition Epidemiology of disease Etiology Pathogenesis and pathophysiology Morphology : it is divided into: -Gross/ macroscopic : visible to the naked eye -Microscopic : visible under a microscope Clinical features/presentation: signs and symptoms Differential diagnosis: is there any other alternative diagnosis/diagnoses with similar findings Treatment and management Prognosis  Pathology Epidemiology Etiology ( cause leads to the beginning of pathogenesis ) Pathogenesis Morphological or chemical alteration Clinical features ( signs and symptoms ) Course of disease The course of a disease is the different stages in the natural history or progression of a disease in the absence of any intervention.  Course of disease The different stages in the natural history or course of a disease especially infectious are as follows: Exposure to A causative agents or risk factors There is a latent period between exposure and onset of disease. The time period from the B exposure to the development of signs or symptoms is called as incubation (induction) period. Onset of disease: the beginning of C signs or symptoms Outcome and consequences of disease: D Following clinical onset, disease may follow any of the following trends: Recovery/resolution of disease without complication or sequalae. Person is back to normal health. The disease recovery but with sequelae. Complications: development of complications in any disease can make things worse. Death.  The Diagnostic Process & The Role Of Pathologist Any patient going to a clinic meets clinician who will take history and do clinical examination. He may ask for radiological and pathological examination in order to come to a diagnosis. The common pathological examinations are blood, urine and stool tests. Sometimes the patient is also asked to undergo a cytopathology or a histopathology test or other special pathological tests in order to obtain an accurate diagnosis. This way pathology plays an essential role in the diagnosis of a disease and management and treatment of patient. Branches/subdivisions Of Pathology Immunohisto- Histopathology Cytopathology Hematology chemistry A study of blood, Study of cell blood cells and A special staining Study of tissue morphology, biopsied/excised bone marrow, used procedure is used exfoliated in the diagnosis of to detect antigens from body or aspirated anemias & in the tissue. from body leukemias.  Branches Of Pathology Chemical pathology/clinical Microbiology Immunology Toxicology biochemistry is the analysis of is the analysis of is the study of Study of various bodily fluids the immune microorganisms. poisonous and (blood, urine, system of the toxic substances. etc) for diagnosis. body. Cytogenetics Molecular Autopsy (clinical genetics) pathology Examples: Examining a dead body 1-Fluorescent in to: is a study of know the cause of death, chromosomal situ hybridization know more about the (FISH) abnormalities. disease, do a research, 2-Southern blot etc.... tests, (will be discussed later) 3-PCR HISTOPATHOLOGY It is the study of tissues using light microscope. Tissues are obtained by doing biopsies and excision of organs by physicians & surgeons. Once the tissue is removed from the patient’s body, it is immediately preserved (fixed) by putting it in a container of formalin (10% formaldehyde). The purpose of fixation is to prevent autolysis and decomposition of the tissue. Tissue is processed in a special multistep way and the end result is very thin slices of stained tissue (4-6 microns) glued on a slide. The most commonly used routine stain is Hematoxylin & Eosin stain. It gives the nucleus a blue/violet color & the cytoplasm a pink color. The pathologist will look at the slide under the microscope and give a diagnosis. Histopathology is usually the final/gold standard of diagnosis. NOTE: sometimes during surgery an urgent diagnosis is needed INSTANTLY and tissue is processed rapidly to give results in 20 minutes. This is called frozen section. HISTOPATHOLOGY (Continued) Preservation Step 2 Excision Step 1 Thin slices of tissue Step 3 Slide is ready Step 3 Step 4 Histopathology slides ready to be examined under a light microscope  CYTOPATHOLOGY Cytopathology is the study of morphology of cells which are obtained by scraping (exfoliative cytology) or aspiration (fine-needle aspiration cytology) from various parts of body. Exfoliative (falling or scrapping off) cytology: or the cells The cells are exfoliate (fall off) scraped of any themselves and collect in the respective mucosa using a fluids/secretion Note: No spatula (e.g. (e.g. sputum and in cervix and oral urinary tract disease) blood seen cavity) the cells which exfoliate collect in the urine etc. CYTOPATHOLOGY (Continued) Fine-needle aspiration cytology (FNAC): In it the cells are The cells obtained obtained by are put on a slide, aspiration/suction stained and of cells from examined affected organ under or tumor a microscope. mass using a needle. CYTOPATHOLOGY (Continued) The morphology of the cells (cytopathology) are studied and a diagnosis made from it. It is used for the purpose of: Screening for cancer (e.g. cervical cytology) is used in Diagnosing cancer the screening of carcinoma of cervix. The advantage of cytologic techniques when compared to histopathological techniques is that the procedure is cheap, takes and requires no anesthesia.  Autopsy It is a sub-specialty of pathology which involves examining a dead body. To provide useful information To do research about various disease. An Autopsy is done to: To determine the cause of death (main so it can be used as a tool to reason why autopsy is done) It can be educate students, surgeons, performed in any of the following situations: etc.... 1-Homicidal 2-Suicidal 3-Accidental 4-To identify the disease Who dose the autopsy? The pathologist  Some instruments in Pathology: There are different diagnostic instruments used in pathology Some of the instruments used in pathology are: Immunofluorescence Light microscope Electron microscope microscope (FI) (IF) microscope uses a special Electron microscope: blue filter and antibodies tagged magnifies up to two with fluorescent green dye to million times, which is identify various antigens in much higher than a light various cells of the body. If microscope. It enables us antigen antibody reaction takes to see cell structure like place the green dye lights up mitochondria, under the IF microscope and endoplasmic reticulum, this way we know that the viral particles etc. It is antigen is present in the cell. It is also called as ultra used in diagnosing structural studies. It is immunological diseases. an expensive technique.  OG THOL Y TEA M PA MCQs 1 Study of cell morphology, exfoliated or aspirated from body? Histopathology cytopathology hematology Immunology 2 What is the term for likely outcome of treatment? prognosis pathogenesis diagnosis Symptoms 3 Which one of the following Pathology techniques uses a blue filter and employs antigens to visualize substances in tissue sections? Molecular Electron Exfoliative Immunofluoresc Biology Microscope cytology -ence 4 You have been asked to classify Parkinson’s disease based on its pathogenesis. Under which of the following categories should you classify this disease? Degenerative Metabolic Infective contagious Answers Key: 1.B 2.A 3.D 4.A  OG THOL Y TEA M PA MCQs 5 What is the gold standard of diagnosis Histopathology Cytopathology Hematology Immunology 6 Is the total number of cases of a particular disease in a particular population in a particular period of time Prevalence Incidence Sequalea Prognosis 7 is a sub-specialty of pathology which involves examining a dead body. Cytogenetics Autopsy Microbiology Toxicology 8 When an urgent diagnosis is needed, and tissue is processed rapidly to give results. this proccess is called exfoliative Frozen Scraping cytology FNAC section Answers Key: 5.A 6.A 7.B 8.D  OG THOL Y TEA M PA Pathology Team 445 TEAM LEADERS : Mohammed Fahad Alruwaily Deemah alotaibi Ruba aldibas Alnoshan MEMBERS WORKED ON THE LECTURE: Abdulaziz Sana Albassam Alshareef