Answer and Discussion of Quiz Set: N-025

5.    Foamy macrophages cannot be highlighted by which of the following techniques?

A.  Immunohistochemistry for CD68

B.  Immunohistochemistry for CD163

C.  Periodic acid Schiff (PAS) stain

D.  Luxol fast blue-cresyl violet

Answer and Discussion: The answer is (D). Macrophages can be effectively highlighted by immunohistochemistry for CD68 and CD163. Lysosomes within macrophages can be positive for PAS stain but this feature is not every consistent and the staining can be subtle. Luxol fast blue-cresyl violet stain is good for demonstration of myelin and neurons. In most circumstances, foamy macrophages can be recognized by morphology with this stain but but Luxol fast blue and cresyl violet does not highly any particular component of foamy macrophages. However, it should be noted that scant and minute myelin droplets in macrophages can be seen in cases with demyelinating diseases.