Pleural effusion in haematological malignancies: an educational position statement.

Pleural effusion is a known complication of haematological malignancies, including lymphomas, leukaemias and multiple myeloma. The true overall incidence of pleural effusion in haematologic disorders is not precisely established, but case series suggest it occurs in roughly 20-48% of patients with these diseases. Among all malignant pleural effusions (MPEs), about 10-16% are attributable to haematologic cancers (especially lymphomas/leukaemias). The development of a pleural effusion in this context poses significant diagnostic challenges, as traditional tests such as pleural fluid cytology or pleural biopsy often have low diagnostic yield. Importantly, the underlying mechanisms of pleural effusion in haematological malignancy are diverse, ranging from direct pleural infiltration and mediastinal nodal obstruction to chylothorax, cardiac dysfunction, and treatment-related complications. These varied aetiologies not only complicate diagnosis but also have direct implications for both immediate and long-term management. Moreover, emerging evidence indicates that the presence of a pleural effusion in patients with haematological malignancies may reflect advanced disease or evolving complications and is often associated with a poorer prognosis. This position statement provides an overview of the prevalence, pathophysiology, diagnostic approach, management strategies, and prognosis of pleural effusions in haematological malignancies, and offers evidence-based recommendations to guide clinical practice.