The international system for reporting serous fluid cytopathology—diagnostic categories and clinical management

• Published in: Journal of the American Society of Cytopathology JASC Vol. 9; no. 6; pp. 469 - 477
• Main Authors: Pinto, Daniel, Chandra, Ashish, Crothers, Barbara A., Kurtycz, Daniel F.I., Schmitt, Fernando
• Format: Journal Article
• Language: English
• Published: Elsevier Inc 01.11.2020
• Subjects: Cytology; Effusion; International system; Molecular pathology; Standardization; Molecular pathology; Effusion; International system; Cytology; Standardization
• ISSN: 2213-2945; 2213-2945
• DOI: 10.1016/j.jasc.2020.05.015

Effusions can develop inside serous cavities in several pathologic states, both neoplastic and non-neoplastic. They are easy to drain and can provide useful diagnostic information. However, the reported diagnostic efficacy of these specimens has not been uniform across different laboratories. To standardize practices, the international system for reporting serous fluid cytology (TIS) was developed in accordance with the best international practices, the most up-to-date reported data, and expert consensus. TIS has set the basic principles for laboratory handling of serous effusion specimens, defined the adequacy criteria, and set a standardized reporting terminology with well-defined criteria for each diagnostic category. These include nondiagnostic, negative for malignancy, atypia of undetermined significance, suspicious for malignancy, and malignant. Each can provide useful inherent information for appropriate clinical management and follow-up, with a defined expected diagnostic category incidence and risk of malignancy. TIS applies to serous fluids collected from the pleura, peritoneal, and pericardial cavities. Using TIS, indeterminate categories are presented as either preliminary or as options of last resource. TIS has emphasized the role of ancillary tests in arriving at the correct interpretation within each category. It also has emphasized the importance of a malignant diagnosis as a definitive diagnosis, comparable to histologic examinations. Because of the well-documented outcomes in the adoption of uniform cytology terminology for other organ systems, we recommend the use of the upcoming TIS and believe its use will be paramount to improving the diagnostic yield in this area of cytology. •To standardize practices, the International System for Reporting Serous Fluid Cytology (TIS) was developed following best international practices, the most up-to-date literature and expert consensus.•TIS sets the basic principles in laboratory handling of serous effusion specimens, defines adequacy criteria and sets a standardized reporting terminology with well-defined criteria for each diagnostic category: non-diagnostic (ND), negative for malignancy (NFM), atypia of undetermined significance (AUS), suspicious for malignancy (SFM) and malignant (MAL).•TIS provides appropriate clinical management and follow-up, with defined expected incidences and risk-of-malignancy (ROM).