Peritoneal washings cytology for the detection of free cancer cells in gastric cancer patients - standardization of sample preparation stages
The detection of free cancer cells (FCC) based on the materials of peritoneal washing of patients with gastric cancer allows to detect peritoneal carcinomatosis and to stage the disease for better treatment management. The correct implementation of all preanalytical stages is an important condition to obtain informative material and for successful detection of FCC. Aim of this study is to increase the informative value of the cytological diagnostic of free cancer cells in peritoneal washings of patients with gastric cancer and to standardize the stages of sample preparation of the material. Material and methods. The material for the study (n=365) was obtained from patients who were examined and treated in the high-tech surgery department of the MCSC named after A.S. Loginov from June 2016 to January 2019. The average age of the patients was 64 years (32-86 years), 178 of them were women and 187 were men. Peritoneal washings were obtained by diagnostic laparoscopy using a standard technique. For samples preparation we used the «liquid» method in a Cyto-Tek (Sakura, Japan) and Thinprep (Hologic, USA) systems and/or by the «cell-block» method and they were stained by Pappenheim or Papanicolaou methods. Results. As a result of 365 examinations, 133 materials (36.4% of cases) with a positive FCC (CY+) were identified. In 229 (62.7%) patients cytological examination was negative (CY-), three cases were not informative (0.9%). We distinguished the following preanalytical stages: obtaining diagnostic material, delivering to the laboratory, performing preparation and staining of the samples. Depending on the size of the precipitate obtained by centrifugation, the material was divided into hypocellular (less than 0.5 ml), normocellular (0.5-1.0 ml) and hypercellular (more than 1.0 ml). In the first and second groups, the study was performed by the «liquid» method and amounted 271 cases (74.2%). The Thinprep was more preferable than Cyto-Tek for samples with low cellularity, contaminated with a significant amount of blood, with a marked histiocytic-leukocyte reaction. The need to store the analyzed samples in the laboratory for more than 2 hours was also a reason to choose The Thinprep. Papanicolaou staining method was finally preferred for the peritoneal washings samples preparation. Conclusions. The choice of methodology based on the results of the primary assessment of the obtained material (sediment volume, probable peripheral blood contamination, etc.) can significantly increase diagnostic value of the cytological examination up to 99.1%.