Histopathology

IMPORTANT DEFINITIONS IN HISTOPATHOLOGY 1. Histopathology- is the study of abnormal human or animal tissues 2. Histopathologic Techniques- deals with the preparation of animal and human tissues thin enough for microscopic studies 3. Exfoliative Cytolgy- entails the microscopical examination and interpretation of cells that are shed spontaneously from epithelial surface or by physical means. Branch of General Pathology, concerned with the detection of cancer and various other pathologic conditions in man through microscopic examination of body fluids and secretions. 4. Biopsy- cutting the cells from living (specimen) person, or it is any piece of tissue or organ removed from operation for diagnosis. TYPES OF BIOPSY a. Surgical or Section Biopsy- is obtaining surgical sections of tissues for histological diagnosis 1. Routine Paraffin (or Celloidin) Method 2. Rush Frozen Section Technique b. Aspiration or Needle Biopsy- consists of the aspiration of cells or particles from tumors for histological diagnosis especially from lumps under the skin like those of breast and neck c. Exfoliative Biopsy- is the examination of fluids from exudates or transudates from serous cavities such as pleura or peritoneum or sputum and urine or bronchial washings. By modern methods of coagulation and sedimentation of the centrifuged fluids from the coagulum can be made into paraffin blocks and resemble regular biopsy specimen. BIOPSY SPECIMENS ARE CLASSIFIED INTO 5 CATEGORIES, NAMELY a. External Growth- the growth removed from the external surface of the body such as a mole b. Surgical Growth- an organ or part of the organ removed from within the human body through an incision such as appendix, tumors of the stomach or kidney. c. Endoscopic Growth- growth removed from within the body by insertion of the instrument through a natural opening such as rectal polyp. d. Puncture- bone marrow sample taken from the puncture into the sternum e. Aspiration- removal of the fluid or soft tissue from the body by insertion of an instrument such as the Vimsivermann’s needle and the subsequent withdrawal of the material for examination. 5. Autopsy- A post mortem examination of dead bodies to determine the cause of death 6. Death- cessation of the tree vital functions of the body that includes: (a) respiratory; (b) circulatory; (c) nervous. SIGNS OF DEATH a. Algor mortis- ot cooling or lowering of the body temperature after death to equalize that of the environment. Body temperature equalized that of the surrounding medium in 16-40 hours after death. b. Livor mortis- or post-mortem lividity is a purplish discoloration of the skin over dependent parts of the body due to congestion and dilation of the veins and capillaries into which blood is driven by contraction of the arteries as well as the diffusion of liberated hemoglobin into the surrounding tissue. c. Rigor mortis- or post-mortem rigidity is the stiffness of skeletal muscle appearing within six hours of death. d. Post-mortem clotting- after death the blood clots. The largest blood clots are formed at the right auricle of the heart as well as the large veins.

e. Post-mortem decomposition (Putrefaction) - is the formation of H2S and other aromatic gases that produce a very offensive odor. NOTE: All these changes are brought about by the generalized invasion of the blood and tissue by bacillus coli and other saprophytes. f. Autolysis- means “self-destruction” and is caused after death of cells by the action of intracellular enzymes whose normal behavior is altered, causing the breakdown of protein and eventual liquefaction of cells. HISTOPATHOLOGIC TECHNIQUES: 1. NUMBERING- is the process of indicating the number of the specimen by means of a pencil in order to properly identify the specimen. Properly speaking it is the first step in all histopathologic techniques. 2. FIXATION- process of preserving cells and tissue constituents in a condition identical to that existing during life and to do this is a way that will allow the preparation of thin stained sections. 3. DEHYDRATION- process of water removal from the tissue prior to replacement by wax, water is immiscible with paraffin or wax. 4. CLEARING OR DEALCOHOLIZATION- is the process whereby the alcohol in the tissue is replaced by a fluid that will dissolve the wax with which the tissue must be impregnated. 5. WAX OR PARAFFIN IMPREGANTION- is the process that involves the impregnation of tissue with a medium that will fill the natural cavities, spaces and interstices of the tissue. 6. EMBEDDING- is the process that involves the use of molds for the purpose of setting the embedding medium to a sufficient consistency in order to allow the cutting of suitably thin sections without undue distortion and without alteration of the spatial relationships of the tissue and cellular elements; facilitates sectioning. 7. BLOCKING- is the process that involves the separation of one tissue block from another using sharp knife (performed only when one uses a compound embedding unit). 8. TRIMMING- the process that involves the cutting of excess wax (in thin slices to prevent the block from cracking) from the tissue block so that the block forms a four-sided prism or truncated pyramid opposite sides being parallel (this is most important if serial sections are desired). 9. SECTIONING- is the process of cutting very thin slices of tissues accomplished with an especially designed instrument called the microtome. 10. STAINING- is the process involving the use of a variety of dyes or stains for the purpose of optically differentiating the cellular and tissue constituents and also to determine the free chemical nature of some details in the cells (histochemical staining). 11. MOUNTING- is the process that involves the use of a medium and a coverslip to facilitate the ease of handling and storage of the slide and to prevent damage to the section. 12. LABELING- the process of indicating the year and specimen number on one end of the prepared side for proper identification.

COMMON TERMS IN THE TISSUE LABORATORY                                 

Acidophilic- readily stained with acid dyes. Alcoholic- a solution in which the solvent is alcohol Aqueous- a solution in which the solvent is water; watery Autolysis- destruction of the tissues by enzymes that are produced by the tissue Artifact- particles or crystals deposited during processing, usually during fixation Accentuators- substances which do not take part in the staining reaction but cause an increase in the selectivity or in the staining power of the dye. Aplasia- is the incomplete or defective development of a tissue or organ Agenesia- complete none appearance of an organ. Atrophy- an acquired decreased in the size of normally developed or mature organ or tissue Basophilic- readily stained with basic dyes Biconcave- having two concave surfaces, what is two surfaces hallowed or rounded inwards Blueing- washing sections in tap water or alkaline solution causing hematoxylin to stain blue; this process normally follows differentiation in acid/alcohol Bevel Angle (27-320)- angle formed between the cutting edge of microtome knife Chatters- horizontal thick and thin ridges appearing in sections Clearing- removal of the dehydrating agent and its replacement with a substance that is miscible with the embedding or mounting medium to be used Clearance Angle (0-150)- angle formed between the surface of the block and the cutting edge of the knife Cytoplasm- the protoplasm of the cell external to the nucleus. Decalcification- the removal of calcium salts from the tissue following fixation Decolorization- the removal of color from stained section; to differentiate Dehydration- the removal of water from a tissue or section Deliquescent- capable of becoming liquid by absorbing moisture from the air Differentiation- the washing out of excess stain until the required color or combination of colors is obtained. Dura Matter- the outer and toughest of the three membranes surrounding the brain and spinal cord Endogenous Pigment- pigment formed within the tissue bu natural means (e.g. melanin) Exogenous Pigment- pigment within the tissue but having their origin outside the body (e.g. tattoos) Embedding- placing a specimen into an embedding medium and causing it to solidify; it is often referred to as casting or blocking. Fixation- the preservation of fresh tissue Fixative- reagent or combination of reagents used to fix tissue Heel- applied to the microtome knife, the end to which the handle is attached. Honing- the action of sharpening a knife by grinding cutting edge, either on a stone or with an abrasive compound. Hypo- synonym for sodium thiosulfate Hypoplasia- failure of an organ to reach or achieve full maturity or adult size Hyperplasia- an increase in the size of an organ or tissue due to an increase in the number of cells

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Inflammation- sum total changes in the living tissues in response to an injurious agent including the local reaction and the repair of injury

CARDINAL SIGNS OF INFLAMMATION a. Rubor (Redness) - due to arteriolar and capillary dilatation with an increased rate of blood flow toward the site of injury and concentration/packing of the red cells in the capillaries causing increased viscosity and slowing of blood flow. b. Tumor (Swelling)- due to increased permeability allowing the extravasation of blood fluid, with increased hydrostatic pressure within the dilated arterioles and capillaries causing localized edema (tumor) c. Calor (Heat)- due to transfer of internal heat to the surface or site of injury d. Dolor (Pain)- due to the pressure upon the sensory nerve by the exudates or tumor e. Functio Laesa (Diminished Function)- due to pain interference with nerve supply and to destruction of the functioning units of the tissue.  Impregnation- the saturation of the tissue with an embedding medium; the deposition of salts of heavy metals on or around tissue tibers during a staining reaction  Metachromatic- a reaction in which a substance is stained a different color to that of the stain employed. This phenomenon is only found in basic aniline dye.  Metaplasia- reversible change involving the transformation in one type of cell to another  Micron- 1/1000th of a millimeter (1/25000th of an inch); unit of measurement for the thickness of sections, the diameter of cells and the size of bacteria ;it is denoted by the symbol µ  Microtome- the machine on which sections are cut  Mordant- a substance which causes a staining reaction to take place by forming an insoluble lake between the dye and the tissue  Nucleus- the darkly staining body within the cell containing hereditary characteristics of the cell and composed of nucleoprotein  Orientation- the precise positioning of the tissue in a block, aligning the block of the microtome or placing a section on the slide  Pawl- a pivoted tongue adapted to fall into notches on a ratchet wheels thus permitting rotating in one direction only  Plano-concave Knife- one side flat and the other side is concave  Protoplasm- the main constituent of all cells, it is a homogenous translucent substances containing water with salts and sugar in true solution, protein in colloidal solution and inorganic salts  Post-chromatization- is the treatment of tissue in 3% aqueous solution of potassium dichromate for 24 hours following fixation and is normally used as a method of mordanting  Progressive Staining- staining each constituent each constituent to a precise color or density without over- staining and differentiating it  Pigment- color or particles imparted to cells and tissues  Quenching- the rapid freezing of tissue during freeze- drying as a means of preservation  Ratchet-wheel –a toothed wheel turned by means of an engaging pawl, a part of a microtome  Refractive Index- the ratio of the velocity of light in air to the velocity of light in a substance  Regressive Staining- technique of over- staining and then washing out or differentiating the excess stain  Scores- tears across a section due to dirt; foreign bodies in the tissue or a “nick” in the knife

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Sections- extremely thin slices of tissue usually 4 to 15 µ in thickness Smear- a thin layer of cell spread out on a microscope slide Stain- a dye or mixture of dyes used to impart color to the substance Staining- the process of coloring the cell, cellular constituents and tissue fibers to facilitate optical differentiation by microscopic examination. Stropping- process of polishing the cutting edge of the knife on leather or canvas done after honing, with toe-to-heel direction Secondary Fixation- term used when tissue are placed in a second fixative to facilitate the demonstration of a specific substance Vacuum Embedding- embedding under negative atmospheric pressure Washing-Out- is the process of removing excess fixative from the tissue after fixation in order to improve staining and remove artifacts from the tissue.