The use of methanol with peroxide is not suitable for which specimens?

• A. Specimens where cell surface markers are to be stained
• B. Frozen sections
• C. Paraffin-embedded sections
• D. Tissues with low antigen density

Answer: (A)

The key idea is how methanol as a fixative affects antigenicity. Methanol with hydrogen peroxide is used to block endogenous peroxidase, but methanol is a strong fixative that can denature or mask epitopes, especially on cell membranes. Cell surface markers are membrane proteins whose conformational epitopes are particularly sensitive to methanol fixation, so antibodies may not bind effectively and staining becomes weak or false-negative. Because of that, this method isn’t suitable when the goal is to detect cell surface markers. It can still be used for other antigen types where surface epitopes are not a limiting factor, depending on the tissue and context.