HT Tissue Processing & Embedding 2 — Questions and Answers
Question 1: Which fixative is most appropriate for preserving glycogen in tissue sections?
- 10% neutral buffered formalin
- Bouin's solution
- Zenker's fixative
- Carnoy's fixative (Correct answer)
Correct answer: Carnoy's fixative
Carnoy's fixative (alcohol-based) best preserves glycogen because it avoids aqueous extraction that occurs with formalin.
Question 2: What is the primary purpose of the clearing step in tissue processing?
- Remove water from tissue
- Remove dehydrant and make tissue miscible with paraffin (Correct answer)
- Harden the tissue for sectioning
- Decalcify bony tissue
Correct answer: Remove dehydrant and make tissue miscible with paraffin
Clearing removes alcohol (or other dehydrants) and renders tissue miscible with molten paraffin wax.
Question 3: A histotechnician notices tissue is crumbly and difficult to section after embedding. Which processing error is most likely?
- Insufficient fixation
- Over-dehydration in absolute alcohol
- Under-clearing with xylene
- Inadequate paraffin infiltration time (Correct answer)
Correct answer: Inadequate paraffin infiltration time
Inadequate paraffin infiltration leaves tissue improperly supported, causing it to crumble during microtomy.
Question 4: Which embedding medium is preferred for processing tissues for enzyme histochemistry?
- Paraffin wax
- Celloidin
- OCT compound with cryostat sectioning (Correct answer)
- Epoxy resin
Correct answer: OCT compound with cryostat sectioning
OCT compound with cryostat sectioning preserves enzyme activity by avoiding heat and chemical processing.
Question 5: When processing fatty tissue such as breast, which modification improves paraffin infiltration?
- Longer fixation time
- Additional dehydration steps at lower alcohol concentrations
- Using multiple changes of clearing agent (Correct answer)
- Reducing paraffin temperature
Correct answer: Using multiple changes of clearing agent
Fatty tissue requires multiple xylene changes to fully remove residual alcohol and fat, ensuring complete paraffin infiltration.
Question 6: Which statement about isopropanol as a dehydrating agent is correct?
- It cannot be used as the sole dehydrant
- It is less toxic than ethanol and acts as both dehydrant and clearing agent (Correct answer)
- It requires a longer schedule than ethanol
- It is incompatible with paraffin wax
Correct answer: It is less toxic than ethanol and acts as both dehydrant and clearing agent
Isopropanol is less toxic than ethanol and, at high concentrations, can act as both dehydrant and clearing agent, eliminating xylene in some protocols.
Question 7: What is the recommended paraffin wax melting point range for routine histology embedding?
- 42–44°C
- 46–48°C
- 56–58°C (Correct answer)
- 62–65°C
Correct answer: 56–58°C
Paraffin wax with a melting point of 56–58°C is standard for routine histology, providing adequate hardness at room temperature for microtomy.
HT Tissue Processing & Embedding 2
Which fixative is most appropriate for preserving glycogen in tissue sections?