The International System for Serous Fluid Cytopathology (TIS) survey in preparation for TIS 2.0

Introduction: The International System for Serous Fluid Cytopathology (TIS) has gained acceptance and has led to literature validating original concepts and suggesting refinements. In preparation for the second edition of TIS, editors generated a survey to solicit experience with and opinions about TIS. Materials and methods: An online survey available from March 8 to June 15, 2024, included 56 questions, offered in 7 languages, related to the practice of serous fluid cytopathology. Results: A total of 598 respondents accessed the survey. Information was collected regarding certification, work setting, work volume and years in practice. In the respondent group, 78% (401 of 513) were pathologists, 18% (92 of 513) cytologists of cytotechnologists, 2% (10 of 513) trainees, and 2% (10 of 513) medical scientists. A total of 23% of participants came from academia. Also, 59% of respondents were (280 of 474) from Asia, 17% Europe, 12% North America, and 10% South America. In all, 61% (287 of 474) have adopted TIS. Over 50% issue a preliminary report awaiting ancillary test results. Another 20% issue such a report depending on circumstance. The most frequent request for refinement of criteria centered around Atypia of Uncertain Significance (AUS). Only small numbers of participants provided data on diagnostic category percentage and risk of malignancy (ROM); however, those that did reported a decrease in nondiagnostic and atypical results with corresponding decreases in ROM for those categories. Variable use of cytochemical and immunocytochemical stains for resolving mesothelial proliferations was reported. Respondents indicated a desire for incorporation of recommendations on clinical management and extension of TIS into body fluid types beyond pleural, pericardial, and peritoneal. Conclusions: This survey examines acceptance of TIS and advice for future directions.