The connective tissue has failed to stain yellow with the Movat pentachrome stain. One possible cause is that the saf ran solution contains water.

• A. Safran solution contains water
• B. The solution was too cold
• C. The tissue was overfixed
• D. The stain pH was too high

Answer: (A)

In Movat pentachrome, the yellow color for connective tissue comes from saffron binding to collagen. The dye is prepared in a solvent that favors proper diffusion and deposition of saffron onto the tissue. If the saffron solution contains water, the solvent environment changes in a way that reduces saffron’s ability to penetrate and bind to collagen, so the connective tissue fails to take up the yellow stain. Using an alcohol-based (or the specified) solvent helps ensure saffron interacts with collagen as intended, producing the yellow color.