ASCP Immunohistochemistry 2

Question 1

What does a negative IHC result on a poorly fixed specimen most likely represent?

Accepted Answer

False negative due to antigen destruction by inadequate fixation

Answer

Inadequate fixation causes protein degradation that destroys antigenic epitopes, resulting in false-negative IHC results even when the antigen is present.

Question 2

In IHC, what is the function of the blocking step with normal serum?

Accepted Answer

To prevent non-specific binding of the secondary antibody to tissue proteins

Answer

Normal serum (from the species used to raise the secondary antibody) saturates non-specific protein binding sites, reducing background staining.

Question 3

Ki-67 IHC is used to assess what cellular property?

Accepted Answer

Cellular proliferation index

Answer

Ki-67 is a nuclear protein expressed only in proliferating cells; IHC for Ki-67 measures the proportion of actively dividing cells (proliferation index).

Question 4

What is the difference between the direct and indirect IHC methods?

Accepted Answer

Direct uses enzyme-labeled primary antibody; indirect uses unlabeled primary and enzyme-labeled secondary antibody

Answer

In the direct method, the primary antibody carries the detection label; in the indirect method, an unlabeled primary antibody is detected by a labeled secondary antibody for greater sensitivity.

Question 5

What IHC marker is used to confirm the presence of muscle differentiation in a tumor?

Accepted Answer

Desmin or smooth muscle actin (SMA)

Answer

Desmin and smooth muscle actin are cytoskeletal proteins expressed in muscle cells; their IHC positivity confirms muscle differentiation in tumor cells.

ASCP - Histotechnician Test Practice Test

ASCP - Histotechnician Test Practice Test

ASCP Immunohistochemistry 2