Proteinase K treatment improves RNA recovery from thyroid cells fixed with liquid-based cytology solution.

K1 cells suspended in CytoRich-Red and CytoRich-Blue, fixatives for LBC, were efficiently recovered by trapping to glass-fiber filters. Importantly, subsequent Proteinase K treatment was essential for efficient RNA extraction from the fixed cells. This finding was also applicable to RNA extraction from CytoRich-Red-fixed thyroid FNAB specimens processed in the same way. Consistently, U6 small nuclear RNA was detected in these RNA samples by reverse transcription-polymerase chain reaction.