In the described staining protocol, control slides may yield poor results if which condition occurred?

• A. The slides have been cut and stored for a long time
• B. The slides were freshly cut
• C. The tissue was fixed in formalin for a short time
• D. The stain solution was expired

Answer: (A)

Control slides are meant to show that the staining process itself is working correctly by reflecting how a properly prepared tissue should look. If the slides have been cut and stored for a long time, the tissue on those slides can dry out and become brittle. That drying can cause sections to crack, detach from the slide, or shrink, leading to uneven staining or loss of detail. These artifacts make the control appear to perform poorly even though the staining reagents and protocol are fine. Freshly cut slides or those stored in appropriate conditions maintain tissue integrity and adhesion, so the control more accurately indicates whether the staining run is sound.