Pathology Dr Vishal Saxena MBBS, MD (Pathology)

What is Pathology? Pathology = “The study of suffering.” Greek Pathos = suffering ; logos = study Involves Study of disease processes and the structural and functional changes in cells, tissues, organs or entire organism that cause or are caused by disease. Explains: The “whys” and “hows” of signs and symptoms manifested by patient. GLOSSARY PATHOLOGY (pathos - logos = the study of disease). The branch of medicine that deals with the nature of disease and its pathogenesis; specifically, the structural and functional changes produced by injury to cells, tissues, organs or the entire organism. Disease: Generally, a departure from health or absence of comfort; specifically, a particular destructive process with a cause and pathogenesis (known or unknown), usually involving tissue changes and characteristic symptoms, signs and course. Injury: A stimulus which damages cells, tissues, or organs; many different types. Lesion: An abnormality in an organ or tissue; the result of an injury or damage; may result in impairment or loss of function. Etiology: The cause of a disease; can be genetic or acquired (the tubercle bacillus is the cause of tuberculosis). Pathogenesis: The process or series of steps by which a cause produces a disease; mechanism. Symptom: A subjective indication of disease; what the patient feels or notices (e.g., pain, dizziness). Sign: An objective indication or symptom of disease; what an observer sees or can measure (e.g., high blood pressure, splenomegaly). Complication: A second disease or abnormal condition occurring during the course of a primary disease. Myocardial infarction is one complication of atherosclerotic coronary artery disease. Cause of Death: The name of a disease, abnormality, trauma or poisoning leading directly or indirectly to death. Manner of Death: NASHU- Natural, Accident, Suicide, Homicide, Undetermined. The way in which death is caused. Diagnosis (dia = between; gnosis = to know): The act or process of deciding the nature of a disease condition by a careful examination of the symptoms and signs; also, the decision or opinion based on that examination. Differential Diagnosis: A list of possible diagnoses Prognosis: A forecast, a prediction of the probable course of a disease and chance of recovery.

The four aspects of disease process: Its cause = etiology The mechanism of its development = pathogenesis The structural changes induced in the cells and organs of the body = morphologic changes Functional consequences of the morphologic changes = clinical significance.

Etiology The cause of a disease. Two major classes of etiologic factors Inherited (e.g. gene defects) Acquired (e.g. infectious, nutritional, chemical, physical)

Pathogenesis The sequence of events that lead to development of disease. i.e. the story from etiology to symptoms and signs.

Morphologic change The structural alterations caused by a disease. Gross (macroscopic) changes: appreciated by naked eye Histologic (microscopic) changes: appreciated by armed eye (microscope) Pathognomonic: means that a particular abnormality is found only in one condition.

Clinical significance Signs and symptoms Disease course and Prognosis Symptom: patients subjective observations. Signs: evidence of disease discovered by physician or abnormalities discovered on physical examination.

Prognosis The expected outcome from a particular disease. Good prognosis: suggests recovery is likely. Poor prognosis: suggests permanent disability or death.

The Science of Pathology Classification General pathology: The study of general reactions of cells and tissues to insults and injuries that are basic to all disease processes. Systemic pathology : the study of specific disease processes or reactions as they affect particular organs or organ systems.

Applied pathology Anatomic pathology Necropsy pathology Surgical pathology Cytopathology Clinical pathology Forensic pathology

Applied pathology Anatomic pathology: Making diagnosis by examining tissues. Necropsy pathology the study of cadavers to elucidate the cause or causes of death. Surgical pathology examination of tissues excised from living patients in an effort to establish a specific diagnosis. Cytopathology the study of individual cells primarily as a method to detect malignant (cancer) cells. FNAC = fine needle aspiration cytology

Applied pathology 2. Clinical pathology analysis of various specimens (whole blood, serum, plasma, urine, feces, spinal fluid, sputum, etc.) from patients to facilitate diagnosis, direct therapeutic approach and monitor therapy. 3. Forensic pathology Subspecialty dealing with medicolegal investigation of death.

Methods in Pathology Biopsy: examination of tissues from the living body to determine the existence or cause of a disease. Closed biopsy: means the pathologist or clinician put a needle into the mass to obtain a bit of tissue (needle or core biopsy) Open biopsy: means an incision was made to obtain a larger mass of tissue. Excisional biopsy: means the mass or entire organ was removed for diagnosis.

Closed or core biopsy

Excisional biopsy

FNAC= Fine Needle Aspiration Cytology A thin bore needle is used to obtain a few cells from a mass lesion. Used for: Superficial mass Deep mass lesions (with help of CT/USG).

FNAC FNAC= Fine Needle Aspiration Cytology ( a thin bore needle is used to obtain a few cells from a mass lesion) FNAC: usually used for superficial masses but now a days in conjunction with ultrasound and CT scan it can be used to obtain cells from deeper masses (for example from liver and lungs) Advantages: quick can be done without anesthesia (except for deeper masses when local anesthesia is given) cheaper does not require admission report can be had in less than two hours

Frozen Sections Done to get a rapid diagnosis while the patient is on operating table. The piece of tissue to be studied is snap frozen in a cold liquid or cold environment (-20 to -70 degree Celsius). Freezing makes the tissue solid enough to section with a microtome. Frozen sections are performed with an instrument called a cryostat. At times during performance of surgical procedures, it is necessary to get a rapid diagnosis of a pathologic process. The surgeon may want to know if the margins of his resection for a malignant neoplasm are clear before closing, or an unexpected disease process may be found and require diagnosis to decide what to do next, or it may be necessary to determine if the appropriate tissue has been obtained for further workup of a disease process. This is accomplished through use of a frozen section. The piece(s) of tissue to be studied are snap frozen in a cold liquid or cold environment (-20 to -70 Celsius). Freezing makes the tissue solid enough to section with a microtome. Frozen sections are performed with an instrument called a cryostat. The cryostat is just a refrigerated box containing a microtome. The temperature inside the cryostat is about -20 to -70 Celsius. The tissue sections are cut and picked up on a glass slide. The sections are then ready for staining.

Stains used in pathology Routine stain: Hematoxylin and Eosin Special stains : examples ……… Hematoxylin (blue) Eosin (Pink) Nuclei Cytoplasm Nucleoli Collagen Bacteria Fibrin Calcium RBC Many others Colloid+ many others

Special stains Mucin stain Mucicarmine,PAS,Alcian blue Melanin stain Fontanna- Mason stain Iron (hemosiderin) Prussian blue stain (Perl’s stain) Fat stain Oil red O Connective tissue stain Trichrome stain Van geison Reticulin Amyloid Congo red

Stains for Microorganisms Gram stain bacteria Warthin Starry silver stain H.pylori Spirochetes AFB stain Ziehl Neelsen method Mycobacterium tuberculosis Faraco Fite stain M. leprae Gomori methenamine silver (GMS) stain Fungi and Pneumocystis jiroveci

PAS (periodic acid Schiff) Stains glycogen, mucin, fungi. Useful for outlining tissue structures Basement membrane and capsules.

Hematologic stains Wright-Giemsa Stain For Peripheral smears Leukocyte alkaline phosphatase stain: To differentiate CML (scant staining) from leukemoid reaction (intense) Tartarate resistant acid phosphatase (TRAP) stain: For hairy cell leukemia Myeloperoxidase, Sudan Black : For myeloblasts

Peripheral blood smear stained with Wright's stain This peripheral blood smear is stained with the Wright's stain.

Immunohistochemical stains Also known as Immunoperoxidase (antibody) stain Cytokeratin – Epithelial cells Vimentin – mesenchymal cells Desmin – Skeletal muscle LCA (CD45)- Lymphocytes CD4/ CD5/ CD8 – T lymphocytes CD19/CD20/CD21-B lymphocytes HMB45 – Melanocytes

Immunohistochemical stains S-100 – Glial tissue Neuron specific enolase (NSE) – neuroendocrine Prostate specific antigen – prostatic epithelium

Stains Used in Cytopathology May-Grünwald-Giemsa (MGG) stain Papanicolaou (PAP) stain Other stains: May-Grünwald stain Giemsa stain Wright stain

Normal PAP smears

PAP smear: Cervical Dysplasia PAP stain: different color of mature and immature epithelial cells, orange-red and green-blue correspondingly

Ancillary techniques Immunofluorescence Renal disease Autoimmune diseases Electron microscopy Neoplasms Molecular techniques Protein electrophoresis Southern blot, Northern blot and Western blot Polymerase chain reaction (PCR)

Immuno-fluorescence A B A: Mycobacteria stained with auramine have a bright yellow appearance with fluorescence microscopy. B: Immunofluorescence techniques can be applied to tissues taken via biopsy. Linear immune deposits along the basement membrane of the glomerulus in a patient with Goodpasture's syndrome. B

Electron Microscopy A B A: Electron microscopy can be useful in identifying fine structure of cells, including their organelles, such as these "happy" mitochondria. B: Electron microscopy can be useful in identifying components of cells that provide a clue to the type of cell. Seen here are neurosecretory granules that indicate the neoplastic cells are from a tumor of neuroendocrine origin, such as this pheochromocytoma. B

Now I lay me down to study I pray the Lord I won't go nutty; And if I fail to learn this junk I pray the Lord that I won't flunk. But if I do, don't pity me at all Just lay my bones in the study hall; Tell my teacher I did my best Then pile my books upon my chest. Now I lay me down to rest, I pray I'll pass Pathology’s test. If I should die before I wake That's one less test I'll have to take!!