Mod 5: HISTOPATHOLOGIC TECHNIQUES Flashcards
This is prepared by cutting a thin slice from a small piece of fixed tissue
Section
What stain is used for viral inclusions?
H&E Staining
What stain is used for Negri Bodies (Rabies)?
Seller’s stain
A machine that fixes, dehydrates, clears, and infiltrates the tissue
Automatic processors
How many steps are in histopathologic techniques?
15 steps
These are samples for the purpose of cytological studies (FNA)?
Fine Needle Aspirations
Primary technique used for diagnosis of “Skin Specimens”
Punch biopsy
This biopsy is you took a portion of the cell and the surrounding tissue.
Used for bone marrow
Core Needle Biopsy
Histological Preparation made from blood, bone marrow, or any fluid such as pleural or ascitic fluid
Smears
This involves swabbing, brushing, lavage, washing, scraping, collection of secretions, shavings, and curettings (layman term of raspa)
Foliative cytology
Usually applied for small samples such as samples that are easily macerated
Whole mount
Whole Mount specimen thickness
No more than 0.2-0.5 mm in thickness
Majority of the preparation in histopathology. It is the cutting of the tissue
Sections
Sections specimen thickness
3-5 mm thick pieces
5 microns thick sections are cut on a microtome
Blocks of tissues taken for processing should be left in __ formalin at __C till processing
This would be fixed in __ hours
10% formalin
60C
2 hours
What is the size of the specimen piece to achieve better penetration of fixative
1cm
Tissues should be fixed in less than __ hour to avoid biochemical changes
less than “1 hour”
These are fixatives that are made up of only one component substance
Simple Fixatives
In Fresh Samples, what type of fixation is required for “electron microscopy”?
Glutaraldehyde fixation
It is the process of the spooning or scooping the tissue out of the endometrial or cervical canal
Curettage
The specimen is washed with __________ to achieve maximum penetration of fixative
normal saline
This is the ability to remove the adipose substrate from any specimen and it is important in the study of lymph nodes
Fat Clearance
2 groups of Chemical Fixatives, classified according to their mechanism of action
Crosslinking Fixative
Precipitating (or denaturing) Fixatives
These are fixatives that are made up of two or more fixatives which been added together to obtain the optimal combined effect
Compound Fixative
Formaldehyde/Formalin Derivatives
“Most widely used fixative for routine histology”
Buffer: pH = 7
Best fixative for “Iron pigments and elastic fibers”
10% Neutral Buffered Formalin
Examples of Simple Fixatives (AAAAMOP)
Aldehydes
Acetic Acid
Acetone
Alcohol
Metallic Fixatives
Osmium
Picric Acid
2 Types of Aldehydes (Cross-Linking Fixative)
Formaldehyde
Glutaraldehyde
Most commonly used fixative in histology, which fixes the tissue by forming cross-linkages in the proteins
Formaldehyde
Difference between “Formaldehyde” and “Formalin”
Formaldehyde: gas produced by oxidation of methyl alcohol
Formalin: made with formaldehyde but the percentage denotes a different formaldehyde concentration
Best fixative for iron pigments and elastic fibers
10% Neutral Buffered Formalin
Formaldehyde/Formalin Derivatives
Simple microanatomical fixative made up of “saturated formaldehyde diluted to 10% with sodium chloride”
Fixation Time: 12-24 hours
Preservation of “lipids”, especially phospholipids
Tissues tend to shrink during alcohol dehydration
10% Formal-Saline
Identify the Formaldehyde/Formalin Derivative based on their application
- Immunohistochemistry and FISH
- Fixation of CNS Tissue and post-mortem tissues
- Immunohistochemistry only
- Routine post-mortem tissues
- 10% Neutral Buffered Formalin
- 10% Formal-Saline
- Zinc-Formalin (unbuffered)
- Formol-Corrosive (Formol-Sublimate)
Formaldehyde/Formalin derivative best for the preservation of “lipids”, especially phospholipids
10% Formal-Saline
Formaldehyde/Formalin Derivatives
Was devised as alternatives to “mercuric chloride” formulations
Zinc Formalin (unbuffered)
Identify the Metallic Fixative
Fixation Time: 4-24 hours
“Brown Pigments” produced due to lysis of RBC (if prolonged fixation)
Zenker-Formol (Helly’s Solution)
Made up of 2 formaldehyde residues, linked by a three-carbon chain.
It has a larger molecule than formaldehyde, thus the rate of diffusion is “SLOW”
Glutaraldehyde