Diagnostic Yield of Malignant Pleural Effusion in Various Primary and Metastatic Cancers: Insights Across Cancer...

Pleural fluid cytology remains a cornerstone in diagnosing malignant pleural effusions (MPEs); however, its diagnostic yield varies considerably across cancer subtypes. This study is aimed at evaluating the diagnostic performance of cytology stratified by malignancy type.

We conducted a retrospective study at a tertiary referral center in Raleigh, North Carolina, enrolling patients aged 18-100 years who underwent thoracentesis for suspected MPE between January 2015 and August 2018. MPE was defined by positive pleural fluid cytology, VATS findings, or histopathological confirmation. Variables analyzed included demographics, cytology results, thoracoscopic findings, and pleural biopsy histopathology.

Of the 779 pleural fluid samples, we included 667 patients (99 malignant and 482 benign); the remaining 86 samples included therapeutic thoracenteses, dry taps, and inadequate volume for cytology. Cytology diagnosed 86 cases of MPE (86.86%), while VATS identified additional eight cases. Overall cytology specificity was 99.8% (95% CI: 99.3%-100%). Adenocarcinoma demonstrated the highest cytologic sensitivity (90.24%), particularly in breast cancer-related MPE (67.44%). Among 482 cytology-negative cases, 130 had documented cancer histories, most frequently lung cancer (17.69%), hematological malignancies (12.30%), and breast cancer (10.76%). Skin and prostate cancers were more likely to yield false-negative cytology results. Malignant mesothelioma requires repeat cytology or VATS for definitive diagnosis in most cases.

Pleural fluid cytology is highly specific and most sensitive for lung and breast adenocarcinomas. Combined cytology and VATS demonstrate superior diagnostic accuracy and should be the standard approach when initial cytology is negative and malignancy remains clinically suspected.