Histopathology PDF - Tissue Processing

HISTOPATHOLOGY Compiled by: Princess Kentana M. Pangilan, RMT UNIT 2: INTRODUCTION TO TISSUE abnormality, but not all. The doctor will slice PROCESSING into the lesion and remove only...

HISTOPATHOLOGY Compiled by: Princess Kentana M. Pangilan, RMT UNIT 2: INTRODUCTION TO TISSUE abnormality, but not all. The doctor will slice PROCESSING into the lesion and remove only a portion of it. If the lesion is found to be cancerous, further Pre-Analytical Factors in Tissue Processing surgery may be needed to remove or excise the Pre-analytical factors are critical for ensuring the quality and accuracy of tissue samples before they undergo entire lesion. analysis. 4. Excisional biopsy generally removes the entire area in question. 1. Warm Ischemia: The time between tissue 5. Punch biopsy is considered the primary removal and fixation, during which the tissue is technique for obtaining diagnostic full-thickness exposed to warm conditions, leading to cellular skin specimens. It requires basic general surgical changes. and suture-tying skills and is easy to learn. The 2. Cold Ischemia: The period during which the technique involves the use of a circular blade tissue is kept at a lower temperature (but not that is rotated down through the epidermis and fixed) before fixation, affecting cellular dermis, and into the subcutaneous fat, yielding a integrity. 3- to 4-mm cylindrical core of tissue sample. 3. Fixation: The process of preserving tissue 6. Shave biopsy where small fragments of tissue structure and composition by using fixatives. are “shaved” from a surface (usually skin). 4. Duration of Fixation: The length of time the 7. Curetting where tissue is scooped or spooned to tissue is exposed to the fixative, which can remove tissue or growths from body cavity such impact the preservation quality. as endometrium or cervical canal. 5. Tissue Exposure to Fixative: Ensuring that all parts of the tissue sample are adequately Once tissues are removed from the body, their proteins exposed to the fixative. and cells are digested and broken down by their own enzymes, independent of a bacterial action. This process 6. Tissue Size and Thickness: The dimensions of is known as autolysis, which is retarded by cold and the tissue sample, which influence the accelerated at room temperature. It is more severe in penetration of the fixative and the overall quality tissues that are rich in enzymes (e.g. liver, brain, and of fixation. kidney) and less rapid in elastic and collagen tissues. 7. Properly Filled-up Surgical Pathology Request: Accurate and complete documentation Methods of Fresh Tissue Examination accompanying the tissue sample for processing. Fresh tissues are usually examined when there is 8. Accessing Procedure: The method used to an immediate need for evaluation. obtain the tissue sample, which can affect the quality of the specimen. 1. Teasing / Dissociation Selected tissue specimen is immersed in a watch glass containing isotonic salt Examination of Fresh Tissue solution / Ringer’s lactate / NSS, Tissues are usually obtained during surgery, carefully dissected or separated, and biopsy, or autopsy. They range from very large examined either unstained or stained specimens or whole organs to tiny fragments of under Phase Contrast Microscope or tissue. Brightfield Microscope. Allows the Advantage: examination at living state, thereby examination of cells in the living state allowing protoplasmic activities such as mitosis, 2. Squash Preparation / Crushing motion, phagocytosis, pinocytosis. Small pieces of tissue not more than 1 Its use is limited because of the fact that tissues mm in diameter are placed in a at fresh state are not permanent and are liable to microscopic slide and forcibly develop changes observed after death. compressed with another slide or with a cover glass; vital stain may be placed at Surgical procedures to obtain specific-type of tissue 1. Fine needle aspiration is the simplest, least the junction of the slide and cover glass invasive test and uses the smallest needle to and allowed to absorb through capillary simply remove cells from the area of action. abnormality. 3. Smear Preparation 2. Core needle biopsy removes not only cells, but Techniques useful in cytological also a small amount of the surrounding tissue. examinations, particularly for cancer This provides additional information to assist in preparation: the examination of the lesion. Streaking – direct or zigzag line by an applicator stick 3. Incisional biopsy takes out even more or platinum loop. Use to obtain relatively surrounding tissue. It takes out some of the uniform distribution of secretion. Too thin or @medtechnotess  HISTOPATHOLOGY Compiled by: Princess Kentana M. Pangilan, RMT too thick are unsuitable. Spreading – maintains cellular interrelationship of the material. Recommended for fresh sputum and bronchial aspirates, and also for thick mucoid secretions. Pull-Apart – place a drop of secretion or sediment upon one slide and facing it to another clean slide. The material disperses evenly over the surface of the two slide. Slides are pulled apart with a single uninterrupted motion. Useful for serous fluids, concentrated sputum, enzymatic GIT lavage, and blood smears. Touch – the surface of a freshly cut piece of tissue is Preparation / brought into contact and pressed on to the Impression surface of a clean glass slide, allowing the Smear cells to be transferred directly to the slide for examination. 4. Frozen Sectioning Tissue can be frozen with liquid nitrogen, isopentane cooled by liquid nitrogen, carbon dioxide gas, or aerosol sprays. A section is examined under the microscope for rapid diagnosis during surgery, and demonstration of cellular architecture and morphological elements. Helps the surgeon in choosing his next plan of action. Recommended when lipids and nervous tissue are to be demonstrated. Usually done on muscle and nerve biopsies. Examination of Preserved Tissue A better and more effective means of studying tissues whether normal or abnormal. Stained for demonstration of specific structures and mounted on glass slides with cover slips for permanent keeping. The aim of good histopathological technique is to produce microscopic preparation of tissue, usually stained, that represent as closely as possible their structure in life. Steps in Processing Preserved Tissue 1. Fixation / Preservation 2. Decalcification 3. Dehydration / Dessication 4. Clearing / Dealcoholization 5. Impregnation / Infiltration 6. Embedding / Casting / Blocking 7. Trimming (optional) 8. Sectioning / Microtomy 9. Staining 10. Mounting 11. Labeling @medtechnotess