Histotechnology Flashcards
also known as numbering
accessioning
1st step in all histopathologic techniques
accessioning
identify properly all the specimens without writing the name of the patient to the accompanying tag of the specimens to be processed
accessioning
Accessioning’s pre-analytical errors
- identification
- material reception
- coding
small pieces of tissue that appear on a slide that does not belong there
floaters
1st and most critical step in histotechnology
fixation
Preserving fresh tissue for examination
fixation
to preserve the morphologic and chemical integrity of the cell in a life-like manner as possible
fixation
primary aim
to harden and protect the tissue from the trauma of further handling
fixation
secondary aim
Give 4 practical considerations of fixation
- speed
- penetration
- volume
- duration of fixation
Penetration: formalin diffuses into the tissue at approximately
1mm/hr
Volume: volume of fixative should be ____ the tissue volume
20 times
True or False
Fibrous organs take longer than small or loosely textured tissues such as biopsies or scrapings
True
2 mechanisms involved in fixation
- additive fixation
- non-additive fixation
Fixation Mechanisms
- non-coagulant cross-linking fixatives
- chemical constituent taken into the cell, forming
- *molecular complexes** and stabilizing proteins
additive fixation
Fixation Mechanisms
- dehydrant coagulant fixatives
- alteration of tissue composition by removing bound water molecule at H bonds within protein molecules
- stabilizes proteins by forming cross-links after water molecule removal
Non-additive fixation
hydrogen ion concentration (pH)
satisfactory fixation
pH 6-8
Temperature
- surgical specimen:
- electron microscopy & histochemical specimens:
- surgical specimen: RT
- electron microscopy & histochemical specimens: 0-4° C
Thickness of Section
- electron microscopy:
- light microscopy:
- electron microscopy: 1-2mm2
- light microscopy: 2 cm2
buffer presence causes polymerization of aldehyde, with consequent decrease in its effective concentration
concentration
Primary fixation in buffered formalin: carried out for ____ during the day the specimen is obtained
2-6 hours
Give 5 fixative categories
- aldehyde
- metallic
- picrate
- osmium troxide
- heat fixation
Mechanism of preservation: cross-linking agents react with proteins and nucleic acids in the tissue
aldehyde fixatives
recommended in immunohistochemical studies
formaldehyde
- produced from oxidation of methyl alcohol
- most common fixative
formaldehyde
- best tissue preservative
- penetrates tissue rapidly
- fiffusion rate = 1 cm in 24hrs
formalin
for CNS tissues & general postmortem examinations
10% formol-saline
best fixative for tissues containing iron pigments
10% BNF (buffered neutral formalin)
Best general tissue fixative
10% BNF
fixative of choice for immunohistochemistry and molecular tests
10% BNF
recommended for routine postmortem tissues
formol-corrosive/formol-sublimate
Allow quick fixation but poor penetration → recommended for electron microscopy
glutaraldehyde
Preservation of lipids
formol-calcium
- excellent trichrome staining
- preservation of cell detail in tissue photography
mercuric chloride
tissues may produce black precipitates
mercuric chloride
- most common mercurial fixative
- fast preservation
- affinity to nuclear chromatin
Zenker’s fluid
Zenker-formol is also known as?
Helly’s solution
preserves cytoplasmic granules
Zenker-Formol (Helly’s solution)
for tumor biopsies of the skin
Heidenhain’s Susa
used for bone marrow biopsies
B-5 fixative