A case report-application of pericardial effusion cytology and next-generation sequencing technology: quick and secure diagnosis of primary effusion lymphoma.

Background: Primary effusion lymphoma (PEL) is an uncommon subtype of non-Hodgkin lymphoma (NHL) that usually involves the pleura, pericardium, and peritoneum without an obvious tumour mass, with multiple plasma effusions as its main clinical feature. We report a case of a massive pericardial effusion in an elderly male with a final diagnosis of PEL. Case summary: A 70-year-old male patient was admitted to hospital with symptoms of chest tightness, shortness of breath, fatigue, loss of appetite, and cough with phlegm after a pericardial effusion had been found for 5 months. The next-generation sequencing of pericardial effusion found human herpesvirus type 8 (HHV-8) infection, and further cytomorphological and immunohistochemical examination were done. According to the patient's HHV-8 infection, the pathological features of heterogeneous B cells with plasmablastic differentiation and the immunohistochemical characteristics of PEL, the final diagnosis was made as human immunodeficiency virus-negative PEL. Discussion: The diversity and non-specificity of PEL symptoms, as well as its rarity, make it difficult to diagnose. In this case, we used the next-generation sequencing technology to screen the pathogen of the patient's pericardial effusion and carried out morphological and immunohistochemical examination of the cells in the pericardial effusion, which provided a clinically operable diagnosis for an uncommon disease, enabling us to make a clear diagnosis faster and start treatment in time.