Spectrum of uncommon malignancies in pleural fluid cytology: A study from a tertiary care center in South India

Background: Pleural fluid cytology is a useful diagnostic test to detect metastasis to pleura. Among the metastatic neoplasms to pleural cavity adenocarcinoma is the most common. However there are other neoplasms which rarely infiltrate pleura and produce effusion. The aim of this study is to analyse the spectrum of these unusual malignancies involving pleural fluid with cytomorphology and ancillary studies. Materials and Methods: This is a retrospective study which includes the pleural fluid samples submitted to the cytology section of our institute between 2015 to 2018. A total of 1510 samples are reviewed. Cases with diagnosis other than adenocarcinoma are selected and their cytomorphological details are analysed with ancillary tests wherever available. Results: Out of 1510 samples analysed, 468 are positive for malignancy. Out of 468, 42 cases are uncommon malignancies. These are classified into hematolymphoid (33/42 cases) which includes Nonhodgkin lyphoma, acute lymphoblastic leukemia, chronic myeloid leukemia, multiple myeloma and nonhematolymphoid neoplasms (9 /42) which includes small round cell tumours, squamous cell carcinoma, small cell carcinoma, germ cell tumor and granulosa cell tumour. Conclusion: There are certain uncommonly encountered malignancies in pleural fluid. Cytomorphology plays a key role in diagnosing them with certain cases requiring ancillary studies to confirm the diagnosis. Keywords: Pleural fluid, Uncommon malignancies, Adenocarcinoma, Cytomorphology.