Introduction To Pathology PDF

INTRODUCTION TO PATHOLOGY Dr. Handan DOĞAN  HISTORY ◦ Pathology is as old as mankind and aims to explain the causes and underlying mechanisms of the diseases ◦ Hippocrates (460-411 B.C.) ◦ Avicenna (İbn Sina) (980-1037) ◦ Morgagni (1682-1771) ◦ Virchow (1821-1905) WHAT IS DISEASE? It ca...

INTRODUCTION TO PATHOLOGY Dr. Handan DOĞAN  HISTORY ◦ Pathology is as old as mankind and aims to explain the causes and underlying mechanisms of the diseases ◦ Hippocrates (460-411 B.C.) ◦ Avicenna (İbn Sina) (980-1037) ◦ Morgagni (1682-1771) ◦ Virchow (1821-1905) WHAT IS DISEASE? It can be; ◦ Congenital or acquired, ◦ Etiology known / unknown, ◦ Occurs by single or multiple factors, ◦ Damages the normal structure of the cell, tissue, or organ ◦ Causes macroscopic or microscopic changes, ◦ Ends with healing or death WHAT IS THE MEANING OF PATHOLOGY? Pathos (suffering) and logia (study of); so it means the study of disease Pathology; 1- The causes of the diseases in organs and systems (Etiology): * Congenital or acquired * Single or multiple factors : - Biological agents (bacteria, viruses), - Physical agents (trauma, burn), - Chemical agents (poisons, alcohol), - Genetic diseases and idiopathic (unknown etiology)  Pathology; 2- Mechanisms of the disease (pathogenesis) : *The answer to the question: How does it happen? - İt is the process that begins with exposure by an agent or microorganism to the onset of that specific disease.  Pathology; 3- Structural changes (morphology): * It can be seen on tissue and organ level by the naked eye, * On cell level by microscope or * On organelle level by electron microscope  Pathology; 4- It evaluates functional defects and their clinical importance and effect on prognosis: *For example; In chronic hepatitis, the activity of the disease and the severity of fibrosis is related to the risk of cirrhosis and the risk of malignancy * Prognosis: Predicting the expected development of a disease and whether it will remain stable, improve or worsen over time. * Morbidity (diseased state), * Mortality (being susceptible): It describes the rate of death caused by a disease in a given population Pathology is mainly divided into 3 categories; 1) Histopathology: examines the tissues Histopathology is an examination performed on the tissue level. A pathologic sample is firstly examine by the naked eye. After that, we examine the tissue parts under the microscope. This is a stomach tumour. And this is what we see under the microscope. Gallbladd er Gallbladder Adenocarcinom a Liver Cirrhosis: Bridging fibrous septa Bone In the empty state, the stomach is contracted and its mucosa and submucosa are thrown up into distinct folds called rugae; when distended with food, the rugae are "ironed out" and flat. Lung Squamous Cell Carcinoma of the lung: ◦ The periphery of a nodule of squamous cell carcinoma. The nearby uninvolved tissue is compressed by the invading tumor front.  Pathology is mainly divided into 3 categories; 2) Cytopathology: examines the cells of tissues and body fluids (easy and cheap) 3) Molecular Pathology: examines molecular structures of the tissues and organs for study and diagnosis of the disease WHAT DOES A PATHOLOGIST DO IN THE ROUTINE PRACTICE? ◦ Diagnosis ◦ Treatment guide ◦ Screening programs ◦ Autopsy DIAGNOSIS ◦ A pathologist is expected to determine or confirm the diagnosis of a patient ◦ For example; determining if a gastric tissue acquired by endoscopic biopsy shows the signs of gastritis, ulcer, or malignancy GUIDANCE OF TREATMENT ◦ The pathologist can change or guide the course of treatment. For example; A patient can undergo surgery whether the report of a pathologic specimen is benign or malignant ◦ The pathologist can determine the effectiveness of a given treatment. For example in gastric ulcers, the physician usually takes a follow-up biopsy after treatment, if the ulcer is healed or not.  SCREENING ◦ Screening of the population for a given disease without any signs and symptoms arise ◦ For example; the PAP smear test for cervical cancer. By these screening tests, we significantly decrease the morbidity and mortality of cervical cancers.  AUTOPSY ◦ An autopsy is performed post-mortem to identify any possible cause of death in forensic medicine ROUTINE PRACTICE IN LABORATORY 1) PATHOLOGICAL SPECIMENS 1. Biopsy 2. Tissues and organs acquired by surgery 3. Autopsy specimens 4. Cytological samples 5. Frozen section  **** BIOPSY * ◦ Small piece of a tissue/organ for diagnostic procedures ◦ Excisional biopsy ◦ Incisional biopsy  **** * BIOPSY ◦Needle Biopsy (Thyroid, lymph node, liver,…)  BIOPSY ◦ By Curettage (endometrium, bone) ◦ Endoscopic/ colposcopic biopsy ◦ Bone Marrow Biopsy  TISSUES AND ORGANS ACQUIRED BY SURGERY ◦ Single or multiple organs are removed by surgery partially or totally ◦ The pathologist evaluates the specimen macroscopically and takes tissue parts from suspicious sites of the sample to send the tissue processing laboratory to be prepared for microscopic evaluation. A gallblader filled with stones  CYTOLOGICAL (SMEAR) SAMPLES ◦ Swabbing mucosa and smearing to a microscope slide (i.e. cervicovaginal smear) ◦ Smearing body fluids (pleura, pericardia, Cerebrospinal Fluid, urine, etc.) on a slide ◦ Diagnosis can be given by directly acquiring cells via the fine needle aspiration, thus eliminating the necessity for a diagnostic surgery (i.e. Thyroid gland aspiration cytology)  Cytolog y ⚫ Cervical cancer and its precancerous lesions can be diagnosed even before it causes any signs or symptoms by cervicovaginal smear. ⚫ Thanks to this method, deaths caused by cervical cancer are very rare. ⚫ In addition, cytological evaluation can provide valuable information about inflammatory changes and infectious agents.  Cytological methods 1) Exfoliative cytology: an examination of the cells shed from the body surfaces. i.e. inside of the mouth… 2) Lavage cytology: Acquiring cells by applying pressure. 3) Fine needle aspiration cytology: Puncturing and aspirating the lesion with a fine needle and smearing on a slide. 4) Intraoperative consultation Papanicolau stain and giemsa stain "FROZEN SECTION" AND INTRAOPERATIVE CONSULTATION ◦ Sometimes during surgery, some special situations occur that can change the course of the operation. In this case, a pathological diagnosis must be given intraoperatively, usually within minutes (i.e. A lesion is identified but it cannot be distinguished whether it is benign or malignant without performing surgery. So the diagnosis must be given during the operation.)  "Frozen section" and intraoperative consultation ◦ If the result is benign -> operation goes as planned, or malignant -> radical surgery is performed (lymph node dissection, etc.) ◦ The tissue is sent to the laboratory as soon as possible. ◦ In this method, the tissue is frozen to -40°C, sectioned by a special device named "cryotome“ and stained by a fast method. ◦ The pathologist evaluates these sections and informs the surgeon generally within 10 to 15 minutes. THE ADVENTURE OF THE MATERIALS REACHING THE LABORATORY  **** 1) RECORDING AND NUMBERING FIRST!!! * ◦ All the samples are given an I.D. after validating the patient name and sample integrity. This I.D. labels the sample at all of the steps in the laboratory from here on (tissue blocks, slides, patient reports).  **** 2) FIXING * ◦ Cells in the unfixed tissue specimens lose their morphological features by the effects of bacterial and self-contained enzymes over time and cannot be used for diagnostic purposes. ◦ Fixing is done to prevent the tissue from degenerating.  **** FIXING* ◦ Special fluids are used for fixing. The most common one is 10 % formalin solution ◦ The minimum fixing solution volume must be no less than 10 times the volume of the specimen ◦ Liquids and cytological materials are fixated by alcohol.  3) MACROSCOPY ◦ Evaluation of external features of the sample ◦ Description of the sample ◦ Measuring dimensions and weight of the sample ◦ Choosing the suspicious and/or necessary tissue parts and taking samples for tissue processing is done in this macroscopy cabinet. Some of the tools we use during macroscopy Measuring dimentions of a colon polyp ◦ Description of the sample: Yellow- white, fatty, have solid areas Taking samples from necessary parts of the tissue and placing them to cassettes for tissue processing Sample preparation for processing Sample preparation for processing  DECALCIFICATION (DEMINERALIZATION) ◦ Softening/removing calcium from tissues like tooth or bone because these rock-solid tissues are impossible to be sectioned without processing.  4) TISSUE PROCESSING ◦ The tissue is processed by special steps (tissue processing) that enables us to take very thin tissue sections (4-5 microns of thickness). The before mentioned cassettes are placed inside this tissue processing device. TISSUE PROCESSING STEPS : a) Dehydration: ◦The water inside the tissue must be removed by using alcohol. ◦Alcohol substitutes the water in the tissue. b) Clearing: ◦Alcohol increases the fragility of the tissue, thus it must be removed. ◦Xylene is used for this purpose. ◦The tissue becomes clear, just like a glass. c) Infiltration: ◦Paraffin must infiltrate the tissue to let it be sliced properly.  5) EMBEDDING ◦ Tissues infiltrated with paraffin are placed in molds along with liquid embedding material (for this purpose, generally heated liquid paraffin is used) ◦ After the mold cools down and hardens, it is finally possible to cut the tissue into thin slices.  molds Solid paraffin is It’s melted by the added device  Liquid paraffin is being filled in the molds After the poured paraffin cools down and hardens, the embedded tissue block is ready. 6) SECTIONING ◦ Paraffin blocks are sectioned into thin slides (generally 4- 5 microns) using a special device named “microtome“. ◦ Sections are put into the water bath to be placed on a microscope slide. ◦ These slides are deparaffinized using heat and xylol, and then rehydrated. tissue blocks tissue blocks are sectioned like this and every piece has a thin slice of tissue. These sections are put into a water bath to be taken on a slide These slides ready to stain  7) STAINING ◦ Routine stain is Hematoxylin and eosin stain (H&E). ◦ There are some advanced staining methods: ◦ Histochemical stains: PAS, Alcian blue, Mason Fontana, oil red,… ◦ Immunohistochemical staining: Cytokeratin,… Staining device This is how the microscopic slides are seen after staining. These samples are ready to be examined under the microscope. 8) MICROSCOPY ◦ Light microscope (most used device routinely) ◦ Immunofluorescence microscope ◦ Electron microscope ◦ Polarized light microscope Light microscope Oral mucosa The surfaces in the oral cavity are lined with stratified squamous nonkeratinized epithelium. The multi-layered epithelium protects the underlying structures from mechanical, chemical and thermal damage. The basal layer is responsible for cell renewal. The oral mucosa has a rich blood supply and in the underlying lamina propria mucosae there is loose connective tissue with numerous capillaries. Scattered lymphocytes are also normally present in the lamina propria. Fingerlike protrusions of connective tissue, termed papillae, fold into the epithelial layer. Underneath the lamina propria is the submucosa with large collagen fibers and elastic fibers, attaching the mucosa to the muscle tissue beneath.  9) DIAGNOSIS ◦ Writing patient report  10) ARCHIVING ◦ Slide archive (at least 20 storage) ◦ Block archive (at least 10 years) ◦ Report archive (at least 20 years) ◦ Specimen (macroscopy) archive Pathologist – Clinicians ◦ We work together ◦ We complement each other ◦ We trust each other’s words and findings  **** PATHOLOGY SAMPLE REJECTION CRITERIAS * ◦ Sample must be taken into an appropriate sample cup ◦ The tissue must be seen easily in the cup ◦ Samples taken from different localizations must be sent in different cups and each sample region must be written on the cup.  PATHOLOGY SAMPLE REJECTION **** CRITERIAS * ◦ Patient name ◦ Patient ID ◦ Sample date and time must be written both on the sample cup(s) and sample form.  PATHOLOGY SAMPLE REJECTION **** CRITERIAS * ◦ The patient form must contain the following information; ◦ Clinical information and initial diagnosis ◦ Lesion localization (left/right, Medial/lateral etc.) ◦ Physician’s signature and contact info ◦ The initial diagnosis is a must (You see the lesion first hand!).  PATHOLOGY SAMPLE REJECTION **** CRITERIAS * ◦ The sample must be sent in sufficient amount of 10% formalin solution (except frozen) ◦ Cytological sample slides must not be broken. ◦ Liquid materials must be transported to the laboratory quickly and fixated in alcohol.  PATHOLOGY SAMPLE REJECTION **** CRITERIAS * ◦ The requested pathological test must be performed by that laboratory ◦ The patient form must be clean and not contaminated with fluids. ◦ Sample transport time must be appropriate, it shouldn’t be delayed.  **** * IRREPARABLE MISTAKES ◦ SAMPLE/SAMPLE CUP mixing (mixing of the cup, patient form, or cup labeling) ◦ Sending the sample without proper fixing or not enough formalin solution therefore the sample cannot be examined.