| What techniques are used for liquid cytology? | Centrifugation (cell block, fixation, tissue processing and embedding) |
| How to get tissue samples? what are the types? | Biopsy
Needle biopsy (0.6-1.5 cm)
Endoscopic biopsy (0.5-5 mm)
Surgical biopsy (excision)
Large surgical specimens (in OR)
partial organ excision, or complete organ excision |
| What are the different technical routine steps? | Fixation, Examination, TIssue processing, Embedding, Cutting and Staining |
| What is fixation? | Essential to preserve cell morphology, should be immediately done after sampling.
Fixation done by formol (LM) and Gluta (EM)
Duration of fixation depends on size, 2-5 hours for biopsy and 24-48 hours for surgical specimens |
| What is tissue processing? | Dehydration by putting it in alcoholic mediums, then remove alcohol and transfer to xylol then heated paraffin at 50 degree infiltrate the tissue.
Takes 12-16 hours, automated process by a machine
For hurry specimens we can make a 3 hour processing but not so reliable |
| What is embedding? | Manual process, heated paraffin is put to freeze in -5 degrees |
| What is cutting? | Using a microtome for very thin sections, 3-5 microns.
Then sections are put on a slide on water drop |
| What is staining? | First remove paraffin, then put stain (nuclear or acidic cytoplasmic stain)
Safaran stains collagen.
A coverslip protects stained tissue
Takes 1 hour or less than 15 min |
| What are frozen sections? | Less than 15 mins, for need of fast decision for surgery, -25 degrees sections are 3-5 micons
Limited since change cell morphology, limited nb of samples submitted, calcified tissues cant be cut.
Used for determine nature of lesions (cancer or inflammatory) |
| What are special stains? | There are two kinds, natural and man-made, aqueous or alcoholic usually
cytoplasmic stains (Eosine (pink), phloxine (manmade, stains acidophillic), Safran (from crocus flower, stains collagen)
Nuclear stains (Carmen (from cochineal flower), Orceine (From lichens) and hematoxylin (from campeche wood, colorless should be oxidized to give a purple color) |
| What is EM? | ➢ Need for a special fixative solution : glutaraldéhyde, …
➢ Embedding in resin
➢ The indications for diagnostic purposes are very limited (abnormalities
of the bronchial cilia, hereditary diseases of the basal membranes of the
skin and of the renal glomerulus) |
