RESUMEN
A significant right-sided pleural effusion was seen on chest radiography in a 53-year-old adult male who complained of bilateral chest pain, shortness of breath, and other additional symptoms. The bloody pleural effusion was removed with a chest tube, and cytopathology analysis showed moderate cellularity. After performing a high-resolution computed tomography, it was discovered that the affected lung had a significant pleural effusion on the right side as well as collapsed and consolidated lung parenchyma. Upon further examination, the right lower lobe wedge biopsy cytology smear revealed mucinous adenocarcinoma. Adults rarely experience a severe malignant pleural effusion brought on by lung adenocarcinoma, particularly in the absence of risk factors.