A lake in histology refers to the combination of which components?

• A. A dye and a mordant
• B. A dye and a solvent
• C. A mordant and a solvent
• D. A pigment and a resin

Answer: (A)

In histology, a lake is an insoluble pigment formed when a dye is precipitated with a mordant, usually a metal salt. The dye provides the color, while the mordant binds the dye molecules together to create a large, water-insoluble complex. This lake then adheres to tissue so the color stays put during staining and handling, giving a durable stain. Solvents by themselves keep the dye in solution, so they don’t form the insoluble lake. A mordant joined with a solvent wouldn’t produce the insoluble pigment either, and a pigment with resin is not the same mechanism used to create a histologic lake.