HTL Immunohistochemistry & Special Stains 3

Question 1

Congo red staining of amyloid, when viewed under polarized light, produces which characteristic appearance?

Accepted Answer

Apple-green birefringence

Answer

Amyloid stained with Congo red exhibits apple-green birefringence under polarized light due to its beta-pleated sheet configuration.

Question 2

Which enzyme is used in the enzymatic antigen retrieval method to unmask antigens in formalin-fixed tissue?

Accepted Answer

Protease K or pepsin

Answer

Proteinase K or pepsin digest protein cross-links formed during formalin fixation to unmask antigenic sites.

Question 3

The Warthin-Starry stain is used to demonstrate which organisms in tissue?

Accepted Answer

Helicobacter pylori and spirochetes

Answer

Warthin-Starry silver impregnation stains spirochetes (including Treponema pallidum) and Helicobacter pylori black against a yellow-brown background.

Question 4

In IHC, DAB (3,3'-diaminobenzidine) chromogen produces which color at the site of peroxidase activity?

Accepted Answer

Brown

Answer

DAB is oxidized by horseradish peroxidase to produce an insoluble brown precipitate at the antigen site.

Question 5

Which IHC panel best differentiates mesothelioma (CK5/6+, calretinin+) from lung adenocarcinoma (TTF-1+, napsin A+)?

Accepted Answer

CK5/6, calretinin, TTF-1, napsin A

Answer

CK5/6 and calretinin support mesothelioma, while TTF-1 and napsin A support lung adenocarcinoma, making this the standard differentiating panel.

(HTL) Histotechnology Certification Practice Test