7 Fresh Tissue Examination & Biopsy + Fixation

Cards (70)

  • Histology is the microscopic study of the normal tissues of the body
  • Histopathology is the microscopic study of tissues affected by disease.
  • Label should be firmly attached to the body of the container—not to the lid of the container
  • Bar codes are frequently used by clinical laboratories.
  • Any discrepancies in specimen identification or labeling should be resolved prior to processing.
  • Biopsy is the ante-mortem examination of tissues or the examination of tissue sample from the living.
  • Fresh tissue does not undergo tissue processing; direct observation under the microscope.
  • Fixed tissue undergoes whole tissue processing before viewing under the microscope
  • Fine needle aspiration is the simplest, least invasive test that uses smallest needle to remove cells from the area of abnormality.
    • Not always adequate to obtain a diagnosis.
    • Will depend mainly on the area to be biopsied.
  • Fine needle aspiration
  • Core needle biopsy removes not only cells but also small amount of surrounding tissue.
    • Provides additional info to assist lesion examination
  • Core needle biopsy
  • Incisional biopsy takes out even more surrounding tissue; slices into the lesion and remove only a portion.
    • Takes out some of the abnormality, but not all.
    • If lesion is found to be cancerous, then further surgery may be needed to remove the entire lesion
  • Excisional biopsy generally removes the entire area in question.
  • Punch biopsy is considered the primary technique for obtaining diagnostic full-thickness skin specimens.
    • Requires basic general surgical and suture-typing skills.
    • Involves the use of a circular blade rotated down through epidermis, dermis, and subcutaneous fat, yielding 3-4 mm cylindrical core tissue sample.
  • Punch biopsy
  • Shave biopsy is where small fragments of tissue are “shaved” from a surface, usually the skin.
  • Shave biopsy
  • Curettings or Curettage is where tissue is scooped or spooned to remove tissue or growths from body cavity such as endometrium or cervical canal.
  • Gross examination consists of describing the specimen and placing all or parts of it into a plastic cassette, in preparation for tissue processing.
    • One of the basis of pathologists' diagnosis.
    • Involves selection of elements that appear to be of clinical significance for histologic examination.
  • Gross examination is also known as the macro examination or gross pathology that refers to the visual inspection and examination of tissues or specimen without a need of a microscope.
  • The purpose of gross examination is to identify any macroscopic abnormalities such as tumor, inflammation, hemorrhage, necrosis, or other structural changes.
  • Findings in gross examination provides important information that guides further diagnostic test, and helps determine cause of disease or death, for comprehensive diagnosis.
  • Two major gross examination processes:
    • Fresh Tissue Examination
    • Preserved Tissue Examination
  • Fresh tissues are usually examined when there is an immediate need for evaluation.
    • They have the advantage of being examined in the living state, thereby allowing protoplasmic activities such as motion, mitosis, and phagocytosis to be observed.
  • Teasing or Dissociation is a fresh tissue exam method where:
    • Tissue is immersed in isotonic salt solution, carefully dissected with a needle, and separated by direct or zigzag spread using an applicator stick.
    • selected pieces of the tissue are transferred carefully to a microscope slide
    • either stained with a supravital dye or examined unstained by phase-contrast microscopy.
  • Teasing or Dissociation
    • Isotonic salt solution used: Normal saline solution or Ringer’s solution
    • Mounted as a wet preparation in microscope, care being taken to avoid forming bubbles
  • Squash Preparation or Crushing is a fresh tissue exam method where tissues less than or equal to 1mm in diameter are pressed between two slides or between a slide and a cover glass.
    • Vital stain is applied between the slides.
    • Viewed using a Phase-contrast or Bright Field microscope.
  • Smear preparation is a process of examining sections or sediments where cellular materials are spread lightly over a slide by means of a wire loop, applicator stick or another slide.
    • Includes streaking, spreading, and pull-apart.
    • This technique is especially useful in cytological examinations especially for cancer diagnosis.
  • Streaking is a smear preparation done with an applicator stick or a platinum loop, the material is rapidly and gently applied in a direct or zigzag line throughout the slide, attempting to obtain a relatively uniform distribution of secretion.
    • Too thin or too thick smears should be avoided.
  • Spreading is a smear preparation where selected portion of the material is transferred into a clean slide and gently spread into moderately thick film by teasing mucous strands w/ applicator stick.
    • A little more tedious than streaking, but has the advantage of maintaining cellular interrelationships of material to be examined.
    • Specially recommended for smear preparation of fresh sputum, bronchial aspirates, and thick mucoid secretions
  • Pull-apart is a smear preparation done by placing a drop of secretion or sediment upon one slide and facing to another clean slide.
    • Material dispenses evenly over the surface of the two slides
    • Two slides are then pulled apart with a single uninterrupted motion, and specimen placed under the microscope for immediate examination or applied with vital stains
  • Touch Preparation or Impression Smear is a special method of smear preparation whereby the surface of a freshly cut piece of tissue is brought into contact and pressed on the surface of a clan glass slide allowing the cells to be transferred directly to the slide for examination by phase-contrast microscopy or staining for light microscopic study.
    • It is also done in frozen section biopsy.
  • Tissue processing describes the various steps required to take the tissue from fixation to the state it is completely infiltrated with suitable histological wax and ready for section cutting
  • Common agents/equipment used in each tissue process:
    • Fixation – formalin
    • Dehydration – alcohol
    • Clearing – xylene/toluene
    • Impregnation & Embedding – paraffin
    • Section-cutting & Trimming – rotary microtome
    • Staining – Hematoxylin-Eosin stain
  • Fixation is the first and most critical step in histotechnology; it is a process that preserves tissues from decay, thereby preventing autolysis or putrefaction.
  • In fixation,
    • The quality of the section on the slide is only as good as the quality of the fixed tissue specimen.
    • A poorly processed tissue will make it difficult for the pathologist to render a proper diagnosis
  • The primary goal of fixation is to preserve the morphologic and chemical integrity of the cell.
    • With fixation, shape structure, intercellular relationship, and chemical constituent of tissues are preserved.
    • It is important to prevent degeneration, decomposition, putrefaction, and distortion of tissues after removal in the body.
  • Formalin preserves the structure of cells & extracellular components by reacting with amino groups of proteins, cross-linking them
  • Fixation preserves the tissues by stopping all cellular activities to view it under the microscope, as if in their original state.
    • They must be placed in a fixative as soon as it leaves the body, because degeneration, decay, autolysis, and putrefaction will occur once the tissue leaves the body