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GASTRIC CANCER CELLS IN PERITONEAL WASHING FLUID: COMPARISON BETWEEN DETECTION BY CONVENTIONAL CYTOLOGY AND LIQUID-BASED CYTOLOGY
Marina A. Pereira, André R. Dias, Gabriel. Kawakami, Amir Z. Charruf, Marcus F. Ramos, Rafael B. Paschoalini, Evandro S. Mello, Ulysses Ribeiro
*Universidade de Sao Paulo Instituto do Cancer do Estado de Sao Paulo, Sao Paulo, São Paulo, Brazil
INTRODUCTION: The presence of peritoneal carcinomatosis (PC) has important implications for the management and prognosis of patients with gastric cancer (GC). Peritoneal washing cytology (PWC) examination with the conversion of CY+ to CY? after chemotherapy has been related to a better survival. However, the sensitivity of conventional cytology (CCY) is still limited. This study aims to evaluate the results of CCY compared to liquid-based cytology (LBCY) with those from tumor tissue samples (peritoneal implant) in patients with suspected PC.
METHODS: PWC samples from 41 patients who were candidates for intraperitoneal chemotherapy from a single-arm prospective phase II trial (NCT05541146) were collected during staging laparoscopy. Ethanol-fixed peritoneal washing was analyzed by CCY (n:41) and LBCY (n:35). Briefly, the samples destined for CCY were fixed with 70% alcohol (1:1), and the sample was subjected to cytocentrifugation in a Cytospin cytocentrifuge. In the LBC, the collected samples were suspended in a liquid medium, and processed in an automated system, where by means of vacuum filtration with a double membrane filter, and cell arrangement in monolayer on the slide.
RESULTS: Among the 41 cases included, 18 had PC. Of these, CY+ was obtained in 3 (16.7%) and 13 (72.2%) of the cases by CCY and BLCY, respectively. The kappa value for the agreement between the histological diagnosis and PWCY was 0.183 (p=0.077) for CCY, and 0.716 (p<0.001) for BLCY. The sensitivity and accuracy of the CCY preparation were 20% and 60.4%, respectively, compared to 72.2% and 85.7% for LBCY preparations, respectively. The median cellularity of CCY samples was 10% (IQR:5-20), and of LBCY samples it was 40% (IQR:30-60). The cellularity was significantly higher in LBCY samples (mean of 27% more cells, p<0.001). LBCY enhanced the diagnosis to CY+ in 28.6% of cases.
CONCLUSIONS: The sensitivity in PWC diagnosis could be improved by LBCY in routine clinical practice, and heighten diagnostic accuracy.
Figure. Microscopy of the peritoneal washing cytology (PWC) by the conventional cytology (CCY) technique in A and B, and the same cases by liquid-based cytology (LBCY) in C and D, where the difference in cellularity, background and detail in the visualization of the cells at higher magnification (20x in B and D) can be observed –
A: Case 1# CCY;
B: Case 2# CCY;
C: Case #1 LBCY;
D: Case #2 LBCY.
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