Histotechnology Applications

SURGICAL PATHOLOGY LABORATORY Surgical Pathology: is the study of lesions of living tissues and cells that are the result of a disease, a trauma , or a malformation  Autopsy :  post-mortem examination to discover the cause of death or the extent of disease. Most of the surgical specimens come from the operating rooms  Others come from emergency rooms or clinics There are two types of specimens:  organs or parts of organs  biopsies  There are various Histotechnological Techniques  Gross techniques  fixation and fixatives  Tissue processing Embedding Microtomy  Staining and mounting  Frozen section  Cytology:  Fine needle aspiration biopsy  Exfoliative cytology  Fixation of cytology material  Processing cytology specimen  Staining of cytology material  Gross Examination : The specimen is properly identified and labeled after its reception in the laboratory. A properly completed surgical pathology request form contains : the age and sex of the patient  essential clinical data type of operation and surgical findings  tissues submitted Steps to examine material in container  General inspection of specimen with identification of all normal and abnormal parts Gross description = type of specimen,structures involved, dimensions, weight, shape, color/ lesion, size, color, consistency, relation with adjacent structures Inadequate gross dissection and sampling will invalidate the microscopic description A crucial part of pathologic examination is dissection, gross description and selection of sections for microscopic study. It cannot be remedied if done poorly at the time of the initial workup. If microscopic description is inadequate, the slide can be reviewed. Gross examination is crucial because the tissue will be sampled and submitted to histology accordingly. The specimen is kept wet for 2-3 months  Fixation  Preserves tissues by stopping autolysis     preservation of morphology by inactivation of molecules (ex: enzymes) that change the morphology of a cell  preservation of the chemical integrity Fixation is accomplished by immersion or perfusion Mechanism of action: modification of spatial configuration of proteins (denaturing) Groups of Fixatives  Aldehydes  Formaldehyde and glutaraldegyde    Mercurials B5 and Zenker's Alcohol: cytology  Oxidizing agents  dichromate fixative and osmium tetroxide  Picrates  Buin's Fixatives  Formalin  is a 10% buffered neutral solution  is made up of 40% formaldehyde (100 ml)    distilled water (900ml) Sodium phosphate, monobasic 4.0 gm Sodium phosphate, dibasic 6.5 gm there is 4% formaldehyde in the final liquid Best general fixative universally used colorless liquid, or colorless inflammable gas with a sharp odor  Immediate irritant to eyes, nose and throat Skin and respiratory system particularly affected Safety precautions include proper ventilation, restricted exposure time and thorough washing if spilled on the skin Formalin fixes by forming methylene bonds between protein chains Tissue Processing  There are 3 sequential steps designed to remove extractable water from tissue specimens and replace it with a medium that solidifies to allow sectioning: Dehydration Clearing Infiltration Processing is done by automatic tissue processor as an overnight schedule that enhances the processing by using heat, vacuum, pressure and agitation Embedding  is the process of surrounding tissue with a firm substance to facilitate the cutting of the sections the mostly used embedding medium is parrafin which has a melting point of 56ºC Stainless steel embedding molds are used for shaping liquid paraffin into blocks Tissues manually removed from the cassette and put into the molds. Paraffin should solidify in around 15 minutes: ready for sectioning Microtomy  The parafin...

Cell is the functional unit of all tissues is the structural unit of all living organisms has the capacity to perform individually all the essential life functions Cell structure Two components: nucleus + nuclear membrane cytoplasm + phospholipid bilayer plasma membrane             Both have subcellular elements called organelles can be looked under : Light microscope Resolving power ≈ 0.25 μm (250 nm) Electron microscope Resolution of structures as small as 3.0 nm (30 Å) Smaller structures seen by biochemical techniques (histochemistry) and immunological techniques (immunohistochemistry) The cell nucleus DNA < 20% Some RNA: messenger, transfer and ribosomal RNA Nucleoprotein associated with DNA: histones (bulk) involved in regulation of DNA activity Chromatin: chromosomes in a different degree of coiling in nondividing nuclei or coiled strands of DNA bound to basic proteins (histones): The DNA is associated with proteins to form chromatin. Nucleolus :spherical structure up to 1 mm in diameter, rich in rRNA and protein. Basophilic on light microscope: H&E. Large nucleoli present in cell proliferation, regeneration, in rapidly growing malignant tumors                       - antihistones