HTL Tissue Processing & Fixation

Question 1

Which fixative is considered the gold standard for routine histological tissue processing?

Accepted Answer

10% neutral buffered formalin

Answer

Bouin's solution

Answer

Zenker's solution

Answer

Carnoy's fixative

Question 2

What is the primary chemical mechanism by which formalin fixes tissue?

Accepted Answer

Cross-linking of proteins via methylene bridges

Answer

Protein denaturation by acid precipitation

Answer

Coagulation of proteins by dehydration

Answer

Lipid saponification

Question 3

The recommended fixation time for a core needle biopsy specimen before processing is:

Accepted Answer

6–72 hours

Answer

Less than 1 hour

Answer

More than 96 hours

Answer

Exactly 24 hours only

Question 4

Which reagent is used in the clearing step of tissue processing, replacing the dehydrant before paraffin infiltration?

Accepted Answer

Xylene

Answer

Ethanol

Answer

Acetone

Answer

Chloroform only

Question 5

What is the purpose of the dehydration step in tissue processing?

Accepted Answer

To remove water so the clearing agent can penetrate

Answer

To remove formalin from the tissue

Answer

To harden the tissue before embedding

Answer

To stain the tissue with eosin

Question 6

Over-fixation in formalin most commonly results in:

Accepted Answer

Poor nuclear staining and masked antigens

Answer

Autolysis of cytoplasmic components

Answer

Excess basophilic staining

Answer

Loss of lipid content only

Question 7

Which fixative is preferred for preserving glycogen in tissues for PAS staining?

Accepted Answer

Alcoholic formalin

Answer

10% NBF

Answer

Zenker's solution

Answer

Glutaraldehyde