ASCP Hematoxylin and Eosin Staining

Question 1

What cellular component is primarily stained by hematoxylin in an H&E stain?

Accepted Answer

Nuclei (DNA/RNA)

Answer

Hematoxylin is a basic dye that binds to negatively charged nucleic acids in the nucleus, staining it blue-purple.

Question 2

What color does eosin stain the cytoplasm and collagen in a routine H&E preparation?

Accepted Answer

Pink/red

Answer

Eosin is an acidic dye that stains positively charged proteins in the cytoplasm and extracellular matrix pink to red.

Question 3

What is the purpose of the mordant in the hematoxylin staining process?

Accepted Answer

To link the hematoxylin dye to tissue components

Answer

A mordant (typically alum) acts as a bridge between the dye and tissue, forming a stable dye-mordant-tissue complex.

Question 4

What is the 'bluing' step in H&E staining intended to accomplish?

Accepted Answer

Convert soluble hematoxylin to an insoluble blue-black complex by raising pH

Answer

Exposure to a slightly alkaline solution (Scott's water or ammonia water) shifts the hematoxylin complex from red-brown to a permanent blue-black.

Question 5

What is the purpose of the differentiation step using acid-alcohol in H&E staining?

Accepted Answer

To selectively remove excess hematoxylin from non-nuclear elements

Answer

Acid-alcohol removes excess hematoxylin from cytoplasm and connective tissue, leaving stain only in the nuclei.

ASCP - Histotechnician Test Practice Test