A retrospective analysis of pleural effusion specimens based on the newly proposed International System for Reporting Serous Fluid Cytopathology

Abstract

Background Recently, the International System for Reporting Serous Fluid Cytopathology (TIS) has been established, with an aim to standardize reporting and guide clinical decision making. Methods The cytological and clinicopathological data of pleural effusions were retrieved from the pathology database and electronic medical records. All specimens were evaluated and reclassified in accordance with the TIS recommendations. Finally, the risk of malignancy (ROM) and performance parameters were measured. Results A total of 2454 pleural effusion specimens were included, among which 30 (1.2%), 1670 (68.1%), 151 (6.2%), 54 (2.2%) and 549 (22.4%) patients were classified into non‐diagnostic (ND), negative for malignancy (NFM), atypia of undetermined significance (AUS), suspicious for malignancy (SFM) and malignancy (MAL) groups, respectively. The most commonly diagnosed malignancies were lung cancer (48.4%), ovary cancer (10.2%), breast cancer (7.5%), and 21.3% unknown primary site (UPS). Among the 36 UPS patients, the most common site of origin was lung (36.1%), followed by ovary (13.9%) and breast (11.1%) via immunocytochemistry of cell block. The calculated ROM values were 26.7%, 12%, 62.3%, 77.8% and 100% for ND, NFM, AUS, SFM and MAL groups, respectively. When considering MAL as the only positive group, the diagnostic accuracy, sensitivity, specificity, positive and negative predictive values were determined to be 95.2%, 81.9%, 100%, 100% and 93.6%, respectively. Conclusion The newly proposed TIS is an easy‐to‐master, user‐friendly, and standardized classification system, especially when applying on pleural effusions. An adequate serous sample, application of immunocytochemistry, review of cytomorphological data and past medical history could enhance the accuracy of cytological diagnosis.

Application of the International System for Reporting Serous Fluid Cytopathology with Cytohistological Correlation and Risk of Malignancy Assessment

“…Other studies have reported mean ROM ranging between 40% and 87.5% for ND, 20.16% and 51.61% for NFM, 39% and 88.23% for AUS, 64% and 87.5% for SFM and 100% for MAL [ 25 , 26 , 28 , 31 ]. Our results are more compatible with the ROM reported by Kundu et al and Xu et al, namely 20% and 26.7% ND, 12% and 16.7% NFM, 50% and 62.3% AUS, 77.8% and 94.4% SFM and, finally, 100% for MAL [ 30 , 32 ]. It seems that the absence of false positives with ROM of 100% in the malignant (TIS5) category is a universal finding.…”

“…Pericardial effusions only included three cases, and their distribution was 33.33% (one case) NFM and 66.67% (two cases) MAL. Our results are compatible with those of other studies [ 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 ], some of which include only pleural effusions [ 25 , 26 , 27 , 30 ], while others include pleural and peritoneal effusions [ 24 , 28 , 31 , 32 ], and one includes only pericardial effusions [ 29 ]. In regard to pleural effusions, the rate of malignancy reported from oncologic centers is significantly higher [ 31 ], while a similar rate to ours is reported from other institutions [ 26 ], probably related to the “general” nature of our institution.…”

“…Meanwhile, for peritoneal effusions, the corresponding values were 80%, 99.3%, 98.5% and 89.6%. The accuracy parameter values are in line with those reported in other studies [ 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 ]. Notably, oncologic centers report lower sensitivity [ 25 , 31 ].…”

“…The most common malignancy in pleural effusions was secondary to breast cancer, followed by lung cancer and lymphoma. A similar order of secondary malignancy origin has been reported by other studies [ 25 , 26 , 30 , 31 ]. A well-developed hematologic clinic in our hospital accounts for the relatively high incidence of lymphomas and leukemias in our series, which, surprisingly, was much higher before the COVID-19 era.…”

Application of the International System for Reporting Serous Fluid Cytopathology (TIS): A retrospective institutional study

“…Our results are more compatible with the ROM levels reported by recent studies. [11][12][13] As highlighted by Pinto et al, 14 Despite being published before the TIS, the terminology used closely approximates that of the international serous system. The results of our performance analysis in pleural, pericardial, and peritoneal effusions are reported in Table 2.…”