Grossing & Fixation in the Histology Laboratory 2 HLAB 1260.pptx

Grossing & Fixation in the Histology Laboratory HLAB 1260 What is Fixation? – In the fields of histology, pathology, and cell biology, fixation is the preservation of biological tissues from decay due to autolysis or putrefaction. – It terminates any ongoing biochemical reaction...

Grossing & Fixation in the Histology Laboratory HLAB 1260 What is Fixation? – In the fields of histology, pathology, and cell biology, fixation is the preservation of biological tissues from decay due to autolysis or putrefaction. – It terminates any ongoing biochemical reactions and may also increase the treated tissues' mechanical strength or stability Title and Content Layout with Chart Contents of a Fixative › Not all fixatives are the same › Some are Aqueous, Non-Aqueous, Additive, Non- Additive › Some fixatives are compound “made of more than 1 chemical reagent” › Contents of Carnoy’s for example: “Carnoy's solution is made of 60% ethanol, 30% chloroform, 10% glacial acetic acid, and 1 gram of ferric chloride” What is Grossing? What is gross dissection › A gross examination, also known as grossing or gross pathology, is a visual inspection of tissue samples with the naked eye to obtain diagnostic information. It's a step in the process of preparing tissue samples for microscopic examination. › During a gross examination, a pathologist or other qualified professional may: › Measure and describe the tissue specimen › Record the size, color, and consistency of the tissue › Inking the margins of the tissue › Select representative areas of the tissue to process into slides. › Dissect the tissue and place cassettes. Macroscopic Examination Dissection of Tissue  Histologists in the Gross Room Grossing stations are the workstations in laboratories where specimens are examined. Grossing workspaces should be well ventilated and staff should wear personal protective equipment (PPE) to minimize the inhalation of formaldehyde fumes From patient to pathologist, preparing tissue specimens for histological examination requires care, skill and sound procedures. This guide provides practical advice on best practice techniques and simple ways to avoid Check Fixation Status › Specimens are dealt with promptly (especially large specimens that may otherwise be inadequately fixed). › No consideration given to optimizing the fixation of problem specimens. › Underfixed Specimens will not process correctly. Prepare Thin Slices › Care is always taken to prepare uniform, thin slices from large specimens (3–4 mm maximum thickness). This is particularly important with dense tissues. › Slices are sometimes 6 mm (or more) thick and are often uneven Avoid Specimen Trauma › Care is taken to avoid traumatizing delicate specimens, particularly those that are incompletely fixed (handle carefully, do not crush, always use sharp blades). › Specimens are handled roughly without any consideration as to their state of fixation. Sometimes blunt blades are used in dissection. Avoid Cross-contamination › Each specimen is handled on a clean surface avoiding the possibility of specimen-to-specimen contamination. › Sometimes the surface of the cutting board is not properly cleaned between specimens. This is of concern when the same specimen types are cut up Step_15_Artefact_spec_to_ one after the other. You do spec_cont_B_1317_croppe d not want to have carry Section of H&E stained over from a specimen that lung containing a piece of is malignant to one that is foreign tissue (liver)  Choose Appropriate Cassettes › Choose appropriate cassettes for the specimen type being processed. Tissue fragments shrink during processing and, if cassette perforations are too large, fragments may escape into processing reagents or, worse still, transfer over to another specimen. › A “one size fits all” approach is used when placing specimens into cassettes.  Avoid Overloading Cassettes › Cassettes are never overloaded with tissue thus allowing ready access to processing reagents and preventing distortion of specimens. If the volume of tissue is too great a second cassette is used. › Cassettes are often crammed full of tissue thus preventing access of processing reagents. Sometimes specimens are distorted in the process.  Clearly Label Cassettes › Cassettes are always clearly labeled. Accurate identification of specimens is of paramount importance. › Sometimes it is difficult to read the labels on cassettes. A bit of guess work may be required. Chicken Liver Gross & Dissection Activity…