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

10% neutral buffered formalin (NBF) is the standard fixative because it preserves tissue morphology, is compatible with most staining techniques, and is cost-effective.

Question 2

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

Accepted Answer

Cross-linking of proteins via methylene bridges

Answer

Formalin fixes tissue by forming methylene bridges (cross-links) between adjacent protein molecules, stabilizing cellular structures.

Question 3

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

Accepted Answer

6–72 hours

Answer

CAP/ASCO guidelines recommend 6–72 hours of formalin fixation for core needle biopsies to ensure adequate fixation without over-fixation artifacts.

Question 4

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

Accepted Answer

Xylene

Answer

Xylene (or xylene substitutes) is used as the clearing agent because it is miscible with both alcohol and paraffin, making tissue transparent and ready for wax infiltration.

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

Dehydration removes water from the tissue using a graded series of alcohols, allowing the non-aqueous clearing agent to penetrate in the next step.

(HTL) Histotechnology Certification Practice Test

(HTL) Histotechnology Certification Practice Test

HTL Tissue Processing & Fixation