Morphological quality and nucleic acid preservation in cytopathology

Background: Fixation is a chemical or physical procedure to prevent the degradation of proteins and tissue morphology. To optimise molecular analysis of archival tissues, it is essential that fixation preserves morphology along with protein epitopes and DNA/RNA integrity. Methods: A new formalin-free alcoholic-based fixative, FineFIX, was used to fix 15 serous effusions and 38 fine-needle aspirates, and cellular morphology and nucleic acid quality were evaluated. Results: The cytomorphology of the effusions and fine-needle aspirates obtained with FineFIX fixation was similar to that obtained with formalin-fixed counterparts. Immunocytochemistry showed comparable results with the traditional fixative, but FineFIX preserved higher-molecular-mass DNA and RNA, as demonstrated by successful PCR of large amplification products of >2000 bp. Conclusions: The formalin-free fixative produced not only satisfactory results for immunocytochemistry on cytological smears and cell blocks, but also excellent preservation of DNA and RNA, which can also be efficiently used for sophisticated molecular techniques.