Med Application of Tissue Processing Flashcards
What are all the steps in tissue processing?
1) Fixation
2) Dehydration
3) Clearing
4) Embedding
5) Sectioning
6) Mounting
7) Staining
What chemical is used in the fixation step of tissue processing?
Formalin
Glutaraldehyde (complex aldehyde)
What is the purpose of the fixation step of tissue processing?
To preserve normal tissue architecture after death. Cross-links the proteins and stabilizes them.
What chemical is used in the dehydration step of tissue processing?
Graded series of ethanol
What is the purpose of the dehydration step of tissue processing?
To remove water from the tissue specimen and replace it with alcohol
What chemical is used in the clearing step of tissue processing?
Xylene
What is the purpose of the clearing step of tissue processing?
Prepares the tissue for the embedding medium (e.g. paraffin)
What chemical is used in the embedding step of tissue processing?
Paraffin
What is the purpose of the embedding step in tissue processing?
The tissue is infiltrated with paraffin so that it is hard enough to section
What is the purpose of the sectioning step in tissue processing?
The tissue is cut into thin sections with a microtome
What is the purpose in the mounting step of tissue processing?
The cut paraffin section is placed on a glass microscope slide
What is the purpose in the staining step of tissue processing?
To impart contrast to tissue structures so that they may be distinguished upon microscopic observation
What are acidophilic structures?
Structures or tissues that have an affinity for negative charge dye.
What are basophilic structures?
Structures or tissues that have an affinity for positive charge dye.
What is H&E?
Hematoxylin and eosin
What structures does the H in H&E dye and in what color?
(Hematoxylin) RNA, DNA, ribosomes, and rER
Blue
What structures does the E in H&E dye and in what color?
(Eosin) Secretory vesicles, sER, lysosomes, mitochondria, and type I collagen
Pink
In Feulgen reaction, what structure does it dye and in what color?
DNA
Magenta
In Mallory triple (trichrome), what structures does it have affinity for?
nuclei, muscle, collagen, hyaline cartilage
In Mallory triple, what color will be imparted on the nuclei?
red
In Mallory triple, what color will be imparted on muscle?
red to orange
In Mallory triple, what color will be imparted on collagen?
blue
In Mallory triple, what color will be imparted on hyaline cartilage?
blue
In PAS reaction, what structure does it have affinity for and what color will be imparted?
Carbohydrates. Magenta
In Osmic acid, what structure does it have affinity for and what color will be imparted?
lipids, black
In Verhoeff stain, what structure will it have affinity for and what color will be imparted?
Elastic fibers, black
In silver methods, what structures will it have affinity for and what color will be imparted?
intermediate filaments of nerve cells, glial cells and reticular fibers. Black
In trypan blue, what structure does it have affinity for and in what color?
macrophages, used on live tissues, blue
In Prussian blue stain, what structure does it stain and in what color?
Hemosiderin (ferric iron), blue
In Nissl stain, what structure does it stain and in what color?
ribosomes, blue
In iron hematoxylin stain, what structures are stained and in what color?
Nuclear elements, chromosomes, mitochondria, centrioles, and muscle striation. Dark blue to black
What stain should you use for coagulative necrosis?
H & E
What stain should be used to detect thickened basement membranes in kidney disease?
PAS
What stain should be used to highlight fibrosis?
mallory triple
What stain can be used to demonstrate nuclear changes in cancer?
feuglen reaction stain
What stain can be used to demonstrate excessive iron accumulation in hemochromatosis?
prussian blue
What stain can be used to identify extracellular deposits of amyloid?
congo red
What stain can be used to detect elastic fibers often found in Marfan syndrome?
Verhoeff
What is metachromasia?
It is a phenomenon in which a given stain imparts different colors to the tissue.
What is immunocytochemistry (immunohistochemistry)?
Technique that uses an antibody tagged with a marker directed to a specific antigen (e.g. fluorescent molecule tagged to a protein associated with the cell or tissue)
What is the direct method of immunocytochemistry?
- Detects presence of antigen, regardless of antigen’s location on cell surface or within nucleus, using an antibody tagged with a marker and specific to the antigen
- Less sensitive than indirect method as fewer antibodies bind to the antigens
What is the indirect method of immunocytochemistry?
- Uses primary and secondary antibodies. The first one is not tagged and is specific to the antigen of interest. The second is tagged and is specific to the primary antibody
- More sensitive as several labeled anti-antibodies can bind to the primary antibody, thus amplifying the signal
What is the medical application of immunocytochemistry?
Used to categorize tumor origins and tumor aggressiveness
What is in situ hybridization?
Identifies a specific genetic sequence
What is the medical application of in situ hybridization?
Used to identify a cell infected with a virus or specific genes on a chromosome. Can also look for extra copies of genes (amplification).
When are frozen tissue sections used?
when urgent tissue diagnosis is needed
What procedure can be used to categorize tumor origin and tumor aggressiveness?
immunocytochemistry
What technique can be used to detect HER2/neu receptors?
immunocytochemistry
What is the goal of in situ hybridization?
to determine whether a known specific genetic sequence is present
What stain should be used to detect glycogen storage disease in alpha1-antitrypsin deficiency in liver cells?
PAS
