A Gelatinous Pleural Effusion as a Diagnostic Clue

Pleural effusion is a common presentation of several pathologies, and the determination of its cause is facilitated by macroscopic, biochemical, microbiological, and cellular analysis. A systematic approach to analyzing the fluid allows for a reduction in clinical diagnoses. Only a select number of diagnoses can be established definitively by thoracentesis, including effusions because of malignancy. We report the case of an 84-year-old male with a right large-volume pleural effusion with an initial diagnostic thoracocentesis demonstrating an exudate with a gelatinous appearance and exudate characteristics. The physical characteristics of the pleural effusion quickly raised the suspicion of mesothelioma, a rare tumor associated with a poor prognosis. In most diseases related to pleural effusion, fluid analysis yields important diagnostic information, and in certain cases, fluid analysis alone is enough for diagnosis. Malignant pleural mesothelioma may present as a viscous pleural effusion with gelatinous characteristics, which may immediately raise suspicion and contribute as a diagnostic clue in the initial study of a pleural effusion. This article was previously presented as a meeting abstract at the 28º Congresso Nacional de Medicina Interna in October 2022.