Pleural Fluid Homing by Anaplastic Large Cell Lymphoma–Cytopathologic Diagnosis of a Rare Presentation

This case highlights the diagnostic value of effusion cytology combined with cell block immunocytochemistry in establishing a definitive diagnosis of ALCL from pleural fluid, even in the absence of an overt mass lesion. Early recognition of this rare presentation is critical for timely management, as effusion-dominant ALCL may portend an aggressive clinical course.