Although 10% formalin is a standard preservative in pancreatic FNAs, the effect of CytoLyt on pancreatic tissue preservation has not been systematically explored.
Smears and cell blocks from CytoLyt-fixed (CF-CBs) and formalin-fixed (FF-CBs) pancreatic FNAs were blindly reviewed without knowledge of the fixative used, and the presence of tissue/tumor autolysis was noted. Controls included FF-CBs from pancreatic FNAs, CF-CBs from nonpancreatic FNAs, and 4 pancreatic FNAs with matched CF-CBs and FF-CBs.
We found that 62 of 85 (73%) pancreatic FNAs with CF-CBs showed significant autolysis, which was most pronounced in acinar cells and/or tumor cells with benign acinar cells in the background, compared with 2 of 46 (4%) FF-CBs (P < .0001) and 3 of 26 (12%) CF-CBs from nonpancreatic FNAs (73% vs 12%; P < .0001). Of the 4 pancreatic FNAs with matched CF-CBs and FF-CBs, all 4 CF-CBs showed marked autolysis versus none of the matched FF-CBs. Of the 23 (27%) pancreatic FNAs with CF-CBs that did not show autolysis, 10 had no acinar cells, and 7 had only minute tissue fragments on CB.
While CytoLyt is a useful fixative for nonpancreatic FNAs it is a suboptimal fixative for pancreatic FNAs and is associated with tissue/tumor autolysis in the majority of cases, influencing morphologic evaluation, and potentially immunocytochemical staining. Autolysis appears to be due to acinar enzymes whose effect is likely interrupted/inhibited by formalin fixation. Cytopathologists and cytotechnologists should be mindful of this pitfall and should avoid using CytoLyt as a fixative for pancreatic FNAs.