Assessing the role of pleural fluid in current cancer diagnostic pathway

Abstract

Pleural fluid will yield diagnosis in approximately 60% of malignant effusions. We aim to review the use of thoracentesis in a NHS District General Hospital, evaluating its role in diagnosis and ability to guide oncological therapy with the help of immunochemistry analysis.

We retrospectively reviewed patients with confirmed malignancy attending our pleural clinic over 2 years using electronic medical records. In patients with confirmed Malignant Mesothelioma (MM) we considered the proportion of patients with accurate cytology on pleural fluid once confirmatory histology available.

Out of the 63 patients with confirmed malignancy diagnosis, pleural fluid yielded a diagnosis in 39 (62%) patients. 34 (54%) patients had sufficient sampling for full immunochemistry and molecular profiling (e.g. ALK , PDL1 and EGFR) on the first pleural sample. The remaining patients underwent subsequent histological biopsy. 18 patients had confirmed MM. 17 patients in this group had pleural effusions amenable to aspiration, of which 11 (65%) demonstrated MM on cytology. Of these, 9 were confirmed with VATS biopsy with the remaining 2 too frail for further investigations. For the 6 patients where cytology did not yield the diagnosis, VATS biopsy demonstrated MM.

Our results show thoracentesis yields a diagnosis of malignancy in 60% patients and provides a sufficient sample to undertake immunochemistry and molecular diagnostics to guide oncological therapy in over half of patients. We found cytology can be used effectively to diagnose MM with high specificity, though a proportion of patients still require biopsy to diagnose underlying malignancy.