Transudative Malignancy: Uncommon and Real.

Light's criteria are the cornerstone to differentiate exudates from transudates. The traditional literature states that malignant pleural effusions are rarely transudative; therefore, cytology tends to be low yield and not a cost-effective decision. This case describes an 82-year-old female who developed a transudative pleural effusion despite having an underlying malignancy, highlighting the importance of integrating clinical judgment into pursuing thoracentesis with the cytological examination.