Pathology Lecture Slides PDF

# Principles of diseases II ## PDT 204 ### VISION COLLEGES ### COLLEGE OF MEDICINE ### L01 - What is Pathology ? #### Objectives * By the end of this lecture, the student will be able to: * Describe the activities of pathologists, including subdivisions of anatomic and clinical pathology. * Describe...

# Principles of diseases II ## PDT 204 ### VISION COLLEGES ### COLLEGE OF MEDICINE ### L01 - What is Pathology ? #### Objectives * By the end of this lecture, the student will be able to: * Describe the activities of pathologists, including subdivisions of anatomic and clinical pathology. * Describe the different methods used in histopathology laboratories. #### What is pathology * Pathology is the **scientific** study of disease. * Pathology embraces the **functional** and **structural changes** in disease, **from the molecular level to the effects on the individual patient** #### Subdivisions of clinical pathology * **Histopathology**: Diagnosis of disease from the examination of **tissues**. * **Cytopathology**: Diagnosis of disease from the examination of **isolated cells**. * **Hematology**: the **study of disorders of the cellular and coagulable components of blood.** * **Microbiology**: the **study of infectious diseases and the organisms responsible for them.** * **Immunology**: the **study of the specific defense mechanisms of the body.** * **Chemical pathology**: the **study and diagnosis of disease from the chemical changes in tissues and fluids.** * **Genetics**: the **study of abnormal chromosomes and genes** * **Toxicology**: the **study of the effects of known or suspected poisons** * **Forensic pathology**: the **use of pathology for legal purposes; e.g., investigation of death in suspicious circumstances.** #### Techniques of Pathology 1. **Gross pathology** (morbid anatomy): **the study of disease by eye**. * Related to radiological changes. 2. **Autopsy: dissection & examination of corpse.** * May be: 1. **Medico-legal autopsies**: **to determine the cause of death and to collect evidence (Forensic medicine)** 2. **Clinical autopsies**: **on patients who died in hospital**: 1. Useful for clinical audit, education, and medical research, mainly for newly discovered diseases. 2. Diagnostic discrepancies are revealed by autopsies in approximately 30% of cases. #### Heart Enlargement (gross & x-ray) The image shows normal heart on left and heart with ventricular hypertrophy on right, as well as an x-ray, all to contrast and point to changes in the heart due to disease,. #### Specimen of testicular cancer Images contrasting testuticular cancer. #### Light microscopy: * Standard technique in **histopathology**. * The sample must first be **thinly sectioned** to permit the transmission of light. * Tissue sections are **stained** to help distinguish between different components. * Standard staining is **H&E** (Hematoxylin & Eosin): * **Hematoxylin**: stains **nuclei** blue (**basophilic**) * **Eosin**: stains **cytoplasm** pink (**Eosinophilic** or **Acidophilic**) Image showing Haematoxylin and eosin stained section of the parotid allowing the serous cells (top right), mucinous cells (left) and salivary duct (lower right) to be readily distinguished. #### Special Staining * Used to detect specific elements or in some fields of pathology. * **Giemsa::** * Useful in identifying parasites or pathogenic bacteria; e.g., H pylori in the stomach * Widely used in blood films (peripheral blood, bone marrow aspirate) * **Papanicolaou stain:** Used for cervical smears * Periodic Acid-Schiff (**PAS)**: Detect glycogen, basement membranes, & in fungal infections. * **Congo Red**: to detect amyloid * **Gram Stain & Ziehl-Neelsen**: in microbiology The images show Giemsa stain with Mast cells in the dermis, and Papanicolaou stain from SCC. The images here show Acute Post-Streptococcal Glomerulonephritis contrasted using H&E stain versus PAS stain. #### Histochemistry * Use of chemical reaction to detect some components in tissues. * Example: acid phosphatase in osteoclasts. * Usually, complex * Not specific * Currently replaced by Immunohistochemistry Figures shows Duray's acid phosphatase technique in Specimen from giant cell tumor of bone fixed in formalin and embedded in paraffin. The osteoclasts show strong acid phosphatase activity. #### Immunohistochemistry (IHC) * Antibodies are created to react with specific substances present in some cells. * Very important tool in current practice. * Usage: 1. **Diagnosis:** * Typing tumors that are poorly differentiated and so are difficult to categorize * Identify possible tumor origin in metastatic * Diagnosis of invasion: Loss of myoepithelial cells (breast cancer) 2. Prognosis (HER2 in breast & gastric cancers) 3. Treatment * ER/PR (Tamoxifen for breast cancer) * HER2 (Herceptin for breast cancer) Image shows HER2 (membranous), CK 7 (protoplasmic), Estrogen Receptor (nuclear) and describes that Antigens may be membranous, cytoplasmic, or nuclear in the body shown in the image. #### Some Examples of Immunostains 1. CD3: T-Lymphocytes 2. CD20: B-Lymphocytes 3. Cytokeratins: Intermediate filaments in epithelial cells 4. Desmin: Intermediate filaments in muscular cells. 5. Ki-67: Cytoplasmic protein in dividing cells. 6. HER2: Receptor on breast cancerous cells. 7. Prostate-specific antigen (PSA): only in the epithelial cells of the prostate #### Histopathology & Cytopathology * **Histopathology** * The primary mode of diagnosis, usually the gold standard for diagnosis. * Use a small piece of tissue. * Required at least 2 days to prepare. * Answer some important questions about the disease: * Tumors: histogenetical pattern, differentiation & grading * Resection margins: Free on not * Lymph nodes * **Cytopathology** * Use a collection of cells that are dissociated from their surrounding tissue. * Useful, but less accurate than histopathology. * Fast (1/2 hour) #### Materials for Histopathology * **Biopsy** * The removal of a sample of tissue for examination under a microscope. * **Types of biopsies** 1. **Excisional biopsy:** A surgical removal of the entire abnormal area for diagnosis (& treatment). Usually for small or superficial lesions. 2. **Incisional biopsy:** A surgical removal of only a portion of an abnormal area for diagnosis. Usually for large lesions and require further treatment. 3. **Endoscopy biopsy:** performed through endoscopy. For lesions in gastrointestinal, respiratory, urinary and genital tracts. * **Fine Needle Biopsy (FNB):** A small amount of tissue is taken for examination by using a hollow needle. Sometimes it is not enough for good diagnosis, such in lymphoma. * **Fine Needle Aspiration (FNA):** use a needle to withdrawal fluid for cytopathological examination. * **Smears:** cells are collected form a superficial surface and smeared on a slide, such as pap smear (from uterine cervix), & blood smear. * **Curettage:** Removal of tissue with a curette from the wall of a cavity or another surface, such as from skin and endometrium. #### Preparation of slides * **Paraffin Wax (standard)** * This is the most popular universally accepted embedding medium for tissue processing. * Cheap and safe. * Tissue blocks and slides can be saved for long duration (years). * Required at least two days to prepare. * **Frozen Section** * Rapid tissue section by cooling the tissue to give immediate report of the tissue sample. * To diagnose the lesions (or its extent) at the time of a surgical operation (30 minutes), and can be used with Immunohistochemistry * Problems: Less accurate, poor morphology, a lot of artifacts, and rapid deterioration rate of the samples. #### References * Rosai and Ackerman's Surgical Pathology (11th ed.) by John R. Goldblum, Laura W. Lamps, Jesse K. McKenney, Jeffrey L Myers Image here showing the front cover of textbook Surgical Pathology Eleventh Edition by John R. Goldblum Laura W. Lamps Jesse K. McKenney Jeffrey L Myers