Effects of formalin vapor exposure on cytological specimens and methods of restoring the damaged staining: NaHCO₃ ameliorates formalin-damaged specimens (1st report)

Abstract

Objectives: In this study, we: 1) attempted to ascertain the effects of formalin vapor exposure on the staining and cell morphology of fixed cytology specimens; and 2) investigated methods of improving the staining. Study Design: We examined smears of cytosol suspensions prepared from uterovaginal secretions. The specimens were exposed to formalin vapor by placing them in a sealed container with a Kim towel soaked in 1 mL of formalin. We also examined the potential of sodium bicarbonate (NaHCO₃) solutions for restoring or improving the staining and cell morphology of formalin vapor-exposed specimens. Results: Exposure to formalin vapor deteriorated the Papanicolaou staining. Among the tested conditions, treatment with 10% aqueous NaHCO₃ solution for 3 h at 60°C improved the staining of the formalin vapor-exposed specimens the most. Conclusion: We demonstrated that exposure to formalin vapor deteriorated the Papanicolaou staining, and that NaHCO₃ solution could partially restore the staining of the specimens. However, cell detachment is an issue that should be considered when treating specimens with aqueous NaHCO₃. Our results indicated that it is imperative for cytology specimens be transported separately from histopathology specimens; alternatively, they should be placed in a sealable plastic bag.