Histopathology introduction

introduction about histopathology

1. HISTOPATHOLOGY – INTRODUCTION PRESENTED BY D. JASMINE PRIYA, B.Sc., DCA., M.Sc., PGDCLT. DR. NGP ARTS AND SCIENCE COLLEGE COIMBATORE

2. CONTENT Introduction Steps In Histopathology 1.Preparation of sample 2.Processing of sample A. Sample collection A. Dehydration B. Fixation B. Clearing C. Infilteration D. Embedding E. Sectioning D. Staining Storage of paraffin blocks

3. INTRODUCTION Histo pathology is an Greek word. Histo – Tissue pathology – disease suffering. Histopathology is the Department of Clinical Laboratory which deals with the study of different types of Tissues. Examination of biopsy or surgical speciamen by a pathologist.

4. STEPS IN HISTOPATHOLOGY PREPARATION OF SAMPLE A. Sample Collection Tissues (with patient history) Bones (with X-ray) Autopsy (consent form) Body fluids CSF (Cerebrospinal fluid ) Skin tissues Etc …… B. Fixation A Chemical process by which biological tissue are preserved from decay either through autolysis or putrefaction.

5. Samples were collected and processed by ‘’FORMALIN’’. Formalin is commonly used fixative in all laboratories. Commonly used fixatives in laboratory 1. 10 % Formalin 2. Formal Saline 3. 10 % Buffered Formalin 4. Bouins Solution 5. Alcoholic Formaldehyde 6. Zenkers Ffluid

6. 2.PROCESSING OF SAMPLE Dehydration Removal of fixative and water from tissue. In most instances, starts by placing in 70% ethanol progressing through 95% to 1 00% ethanol. For delicate tissues ( sembryonic  tissues), start with & 80% ethanol Dehydrating agent should not be less than 10 times the volume of the tissue Commonly used dehydrating agents Alcohol Acetone Diethylene dioxide

7. B. Clearing Clearing is required to remove alcohol from tissues and is replaced by fluid which is miscible  with wax with which tissue must be impregnated Clearing agent is miscible with both dehydrating agent as well as paraffin wax Commonly Used Clearing Agents In Laboratory Benzene Xylene Toluene Choloroform Petroleum ether Oil of wintergreen (Methyl salicylate) Cedar wood oil Carbon tetrachloride Dioxane Aniline oil    

8. C. Infilteration /Impregnation Infiltration/impregnation. The role of the infiltration agent is to remove the clearing agent from the tissue and to completely permeate the tissue with paraffin wax. This will allow the tissue to harden and produce a wax block from which thin histological sections can be cut. Commonly used infilteration medium Paraffin is the most commonly used medium for infiltration, embedding and formation of tissue blocks .

9. D. Pre embedding / Embedding Once tissue samples are infiltrated by paraffin they are removed from the casettes and carefully positioned inside a metal base mold. The mold is filled with melted paraffin and then immediately placed on a cooling surface. In this manner the cassette will be used as a base of the paraffin block of microtome sectioning . E. Sectioning The paraffin block is mounted on the microtome holder. Sections are cut as a ribbon and floated on hot water bath maintained at 45*C to stretch the paraffin section. Tissue section are then allowed to dry at room temperature or 37*c.

10. At the end of the processing the sample is inserted into molds and covered with liquid paraffin. Then, the cassette with the identification number of the patient and additional paraffin is placed on the mold. The mold is then laid on a cold surface in order to favor its solidification and subsequent creation of the block. Types Of Mold Paper mold Metal mold Dimmock mold Disposable mold (plastic) Metal or plastic mold used for ring cassettes (F) or standard cassettes (G)

11. F . Staining Methods 1. PAP staining This method is used to differentiate cells in the smear preparation of various gynecological specimens (pap smears), materials containing exfoliative cells and material from fine needle aspiration. Papanicolaou stain includes both acidic and basic dyes. Acidic dye stains the basic components of the cell and basic dye stain the acidic components of the cell. The polychromatic PAP stain involves  five dyes in three solutions . Hematoxylin  Orange Green 6  Eosin Azure  Light green SF  Bismarck brown Y  Nuclei : Blue Acidophilic cells : Red Basophilic cells : Blue Green Erythrocytes : Orange-red

12. 2. Hematoxylin and Eosin (H&E) staining :  This is a classic standard tissue section staining method widely used for the inspection of tissue components for pathological analysis that’s applicable in all organs and disease models. based on binding of nucleic acid and other acidic components of the tissue to the basic hematoxylin stain. The acidic counter stain, eosin, binds to basic components in the tissue, such as cytoplasmic proteins . 3. TBS ( Toluidine blue staining):  This method is used for staining of mast cells that are found in the connective tissue and their cytoplasm contains granules composed of heparin and histamine. Following Toluidine staining, mast cells are stained red-purple and the background is stained blue

13. STORAGE OF TISSUE SLIDES OR PARAFFIN BLOCKS The tissue slides or paraffin blocks are store with sufficient space between them in a dry and reasonably air tight boxes in a fridge (4*C) for a month.