BACKGROUND: Primary effusion lymphoma is a rare, high-grade non-Hodgkin's lymphoma that usually occurs in immunosuppressed or human immunodeficiency virus-positive individuals in advanced stages of the disease. However, primary effusion lymphoma occasionally affects immunocompetent patients who are infected with human herpes virus type 8 or Epstein-Barr virus. This disease manifests with liquid collections in cavities, producing constitutional symptoms; fever; weight loss; and symptoms related to extrinsic compression, such as dyspnea or abdominal discomfort. Diagnosis is confirmed with cytological or tissue evaluation showing large, multinucleated lymphoid cells with positive specific markers for the disease, such as CD45 and markers related to viral infections, when present. There is no standard treatment for primary effusion lymphoma, but several chemotherapy protocols are recommended, usually with poor results. CASE PRESENTATION: We present a case of an adult human immunodeficiency virus-negative Hispanic origin woman with primary effusion lymphoma with pleuritic, pericardial, and peritoneal compromise who also had unusual complications during a diagnostic procedure: the accidental rupture of the left ventricle and the development of a secondary left ventricular pseudoaneurysm. We describe the clinical, radiological, and laboratory characteristics as well as the outcome of this case. CONCLUSIONS: Primary effusion lymphoma is a very rare entity that represents 4% of non-Hodgkin's lymphoma cases associated with human immunodeficiency virus and 0.1% to 1% of all lymphomas in patients with another type of immunodeficiency in regions where human herpes virus type 8 is not endemic. This reported case is an unusual presentation of primary effusion lymphoma because it occurred in an immunocompetent human immunodeficiency virus-negative adult woman without the presence of Kaposi's sarcoma or Castleman's disease and for whom the clinical course after chemotherapy was successful. However, the rupture of the free wall of the left ventricle is a very rare catastrophic event that usually occurs after myocardial infarction. Left ventricle free wall rupture rarely goes unnoticed, but when it occurs, it leads to the development of a ventricular pseudoaneurysm in which the rupture is contained by the pericardium with an organized thrombus and an adjacent hematoma.