Which statement best describes the color-to-substance relationship in this image?

• A. Red corresponds to mucin
• B. Red corresponds to collagen
• C. Red corresponds to nuclei
• D. Red corresponds to lipids

Answer: (A)

In this staining scenario, color maps directly to a specific tissue component. The red coloration is produced by a mucicarmine stain, which specifically binds to acidic mucopolysaccharides in mucin found in goblet cells and mucus secretions. That binding yields a deep red that stands out against the counterstain, making mucin easy to identify. So the red areas indicate the presence of mucin.

Nuclei usually appear blue or purple with hematoxylin, not red. Collagen can appear blue or green depending on the stain used, and lipids are not red in routine paraffin sections unless a lipid-specific method is employed. Thus, the red in this image best corresponds to mucin.