CY0-to-CY1 Conversion in Gastric Cancer Peritoneal Lavage Cytology: Clinical Significance and Improved Cell Retention by Et + PA Fixation.

Peritoneal lavage cytology (PLC) is important for staging gastric cancer, but intraoperative assessment may miss malignant cells because only a limited portion of the specimen can be examined. We retrospectively analyzed 287 patients who underwent gastrectomy with intraoperative PLC between 2014 and 2022. Cytologic status was classified as CY-, CY0-to-CY1 conversion, or CY+ based on intraoperative and permanent cytologic findings. Of 287 patients, 251 were CY-, 10 showed CY0-to-CY1 conversion, and 26 were CY+ on intraoperative assessment, resulting in 36 final CY1 cases. Patients with CY0-to-CY1 conversion had significantly worse overall survival than CY- patients and outcomes comparable to those of CY+ patients. Serosal invasion/pT4 disease was strongly associated with final CY1 status and was frequent among conversion cases. In a separate technical evaluation, brief ethanol fixation followed by polyethylene glycol and acetone-methanol fixation (Et + PA fixation) significantly improved total cell retention and preservation of tumor-cell clusters compared with conventional ethanol fixation in 11 paired cases. CY0-to-CY1 conversion represents clinically meaningful cytology-positive disease. Et + PA fixation improves cellular retention during cytologic preparation and may improve the quality of intraoperative PLC preparations.