An unusual cause of pleural effusion

We describe a case of human herpes virus‐8‐associated primary effusion lymphoma (PEL) in a patient initially presented with fever, non‐productive cough and exertional dyspnoea. Physical examination revealed oral thrush, diminished breath sounds and dullness on percussion over the left hemithorax. A thoracic computed tomography (CT) revealed left‐sided massive pleural effusion without tumour masses or lymphadenopathy. The effusion was drained and cytology showed medium to large lymphoid cells, with prominent nucleoli and irregular nuclear contours. Meanwhile, his HIV was tested positive. Cell block immunostaining of the pleural effusion revealed these cells were CD45 (+), CD30 (+), MUM1 (melanoma‐associated antigen [mutated] 1) (+), LANA (latency‐associated nuclear antigen) (+) and EBER (Epstein–Barr virus‐encoded small RNAs) in situ hybridization (−). This case highlights the learning point that PEL in the setting of HIV/AIDS should be added in the differential diagnosis of patients with unexplained oropharyngeal candidiasis and malignant lymphomatous pleural effusion without a clear primary site.