INTRODUCTION: Cytologic evaluation of pericardial fluid is essential for diagnosing malignant pericardial effusions secondary to metastatic disease and for guiding appropriate clinical management
however, large cohort and up-to-date studies on malignancy rates and distribution of primary tumor sites is lacking. MATERIALS AND METHODS: A retrospective analysis of pericardial fluid specimens from 2 large academic medical centers over a 10-year period was conducted. Clinical and specimen characteristics were correlated with cytologic diagnoses, and compared with surgical pathology pericardial specimens when available. In addition, genomic testing results were examined in a subset of malignant cases. RESULTS: A total of 1667 pericardial fluid specimens were evaluated, with 15.3% diagnosed as malignant. Lung cancer (50.6%) was by far the most common primary tumor causing malignant pericardial effusions, followed by breast (13.0%), hematolymphoid (12.6%), and gastrointestinal (6.1%) cancers. A subset of patients with paired cytology and surgical pathology pericardial specimens showed concordance in 84.2% of cases, with discordant cases more frequently presenting with a positive cytology but negative surgical pathology result. Genomic analysis of a subset of malignant pericardial effusions revealed the most frequently mutated genes to be TP53, KRAS, CDKN2A/B, and PIK3CA, with a larger proportion of high tumor mutational burden (≥10 muts/Mb) in pericardial fluid samples compared to primary or metastatic sites. CONCLUSIONS: While lung cancer is the most frequent cause of a cytology-confirmed malignant pericardial effusion, familiarity with relative frequencies of metastases from other sites can be particularly helpful, especially in the diagnostic work-up of an occult malignant pericardial effusion.