Abstract We report the case of a 71-year-old man, without any previous history of cardiovascular disease, who was derived to our echocardiography laboratory because of a six-month period of dyspnoea. In the echocardiographic examination, various pleural masses which depended from the left visceral pleura were found, surrounded by, what it seemed, an abnormally located severe anterior pleural effusion, which caused left lung atelectasis (jellyfish sign, complete atelectasis of a lung lobe which floats above a massive pleural effusion) with a less important pericardial effusion (Figure 1). After the echocardiographic findings, a total body Computed Axial Tomography (CAT) scan and a Positron Emission Tomography (PET) were performed, confirming various left pleural implants and a severe left pleural effusion causing a big left lung atelectasis with widespread cervical, thoracic and abdominopelvic adenophaties, suggestive of advanced lymphoma. The cytological exam of the pleural liquid obtained by the thoracentesis procedure, showed a monotonous population of predominantly medium size cells with signs of nuclear indentation compatible with a pleural affection by a germinal center follicular lymphoma. Pleural effusion is a common complication of lymphomas (20-30%) and is considered as one of the factors adversely influencing overall survival, as in most of the cases, serous cavity involvement is part of a disseminated disease process. The thoracic duct obstruction and impaired lymphatic drainage appear to be the primary mechanism for pathogenesis of pleural effusion in Hodgkin´s disease and direct pleural infiltration is the predominant cause in non-Hodgkin´s lymphoma. Because the descending thoracic aorta is interposed between the pericardium anteriorly and the pleura posteriorly, echocardiography may be a useful landmark in the differentiation of posterior effusions. However, sometimes due to the abnormal position of the effusion, it might be difficult to differentiate between pericardial and pleural effusions, with the need, as in our case, to perform a multi-modality imaging study with a CAT and PET scan, followed by a cytological exam, to confirm the diagnosis and to guide the posterior treatment. Finally, we would like to underline the importance of familiarizing ourselves on the basics of pulmonary echocardiography, as these findings are frequent during the performance of echocardiography in our daily practice. Abstract P1735 Figure. Jellyfish sign in pleural effusion