ASCP Tissue Processing 1 — Questions and Answers
Question 1: What is the primary purpose of fixation in tissue processing?
- To prevent autolysis and preserve tissue morphology (Correct answer)
- To dehydrate tissue for embedding
- To remove lipids from tissue
- To decalcify bone specimens
Correct answer: To prevent autolysis and preserve tissue morphology
Fixation prevents autolysis and microbial decomposition by cross-linking proteins to preserve tissue architecture.
Question 2: Which fixative is considered the gold standard for routine histological processing?
- Bouin's solution
- Zenker's fixative
- 10% neutral buffered formalin (Correct answer)
- Glutaraldehyde
Correct answer: 10% neutral buffered formalin
10% neutral buffered formalin is the standard fixative because it preserves morphology well and is compatible with most downstream staining techniques.
Question 3: What is the purpose of the dehydration step in tissue processing?
- To remove fixative residue
- To remove water before infiltration with paraffin (Correct answer)
- To enhance nuclear staining
- To clear pigments from tissue
Correct answer: To remove water before infiltration with paraffin
Dehydration removes water from tissue using ascending grades of alcohol so the tissue can be infiltrated with paraffin wax.
Question 4: Which reagent is commonly used as a clearing agent to remove alcohol before paraffin infiltration?
- Acetone
- Xylene (Correct answer)
- Ethanol
- Methanol
Correct answer: Xylene
Xylene is miscible with both alcohol and paraffin, making it the standard clearing agent in tissue processing.
Question 5: What processing artifact results from inadequate fixation before processing?
- Chatter artifact
- Retraction artifact
- Autolysis (Correct answer)
- Folding artifact
Correct answer: Autolysis
Inadequate fixation allows continued enzymatic activity, leading to autolysis and degraded tissue morphology.
Question 6: What is the recommended tissue thickness for routine formalin fixation to ensure adequate penetration?
- 5–10 mm (Correct answer)
- 1–3 mm
- 15–20 mm
- 20–25 mm
Correct answer: 5–10 mm
Tissue sections of 5–10 mm allow adequate formalin penetration within the recommended fixation time.
ASCP Tissue Processing 1
What is the primary purpose of fixation in tissue processing?