The appropriate control tissue for Mayer mucicarmine staining should be which of the following?

• A. Autolyzed colon, small intestine or appendix
• B. Unautolyzed colon, small intestine or appendix
• C. Autolyzed stomach tissue
• D. Fresh frozen tissue only

Answer: (B)

Mayer mucicarmine staining highlights acidic mucins in goblet cells, so a reliable positive control must have preserved mucin content. Autolysis disrupts mucin and goblet cell integrity, leading to weak or inconsistent staining and a poor control. Therefore, tissue from colon, small intestine, or appendix that is unautolyzed provides the appropriate context because it contains goblet cells with intact mucin that will reliably take up the magenta stain when fixation and processing are proper. Autolyzed tissue would not demonstrate the stain accurately, and stomach tissue can have different mucin patterns that make it less dependable as a control. Fresh frozen tissue is not the standard for this paraffin-embedded staining method and can yield variable results.