Which staining method is used to detect calcium in tissue?

• A. Van Kossa
• B. Mucicarmine
• C. Ziehl Neelsen
• D. Gomori's Aldehyde Fuchsin

Answer: (A)

Calcium deposits in tissue are revealed by a histochemical reaction that makes calcified areas stand out with a dark color. Van Kossa uses silver nitrate to react with the phosphate (and related calcium salts) in the tissue, and the silver is reduced to metallic silver at those sites. The result is a dark, typically black, deposit where calcification is present, against the lighter background of the section. This direct dark marking of calcium salts is what makes it the method of choice for detecting calcium in tissue.

The other stains target different things. Mucicarmine highlights mucins and related glycopolymers, not mineral deposits. Ziehl-Neelsen is used for acid-fast bacteria. Gomori's aldehyde fuchsin stains other tissue components, such as elastic fibers or specific proteins, but not calcium salts. So the Van Kossa stain is the correct choice because its chemistry specifically marks calcium-containing minerals as a dark precipitate.