BACKGROUND: Primary mediastinal diffuse large B cell lymphoma (DLBCL) presenting as a large intracardiac tumor is extremely rare and has not been significantly reported in the literature. Cardiac lymphoma consists of 2 subtypes: mediastinal DLBCL invading the heart and primary cardiac lymphoma. Both subtypes have a poor prognosis and are treated similarly. Mediastinal DLBCL is a life-threatening condition that, if diagnosed early, has a better survival rate. This is a rare case of a mediastinal DLBCL invading the right atrium as a large intracardiac mass, causing partial obstruction of the tricuspid valve without hemodynamic compromise.

CASE REPORT: A 57-year-old female presented with unintentional weight loss, fatigue, exertional dyspnea, and cough for 8 weeks. Transesophageal echocardiogram showed a mass (3.5×3.5 cm) in the posterior wall of the right atrium partially obstructing the tricuspid valve. Biopsy revealed DLBCL. Given new-onset lymphoma, a human immunodeficiency virus (HIV) test was done and came back positive. CD4 count was 100 cells/mm³. Chemotherapy was initiated with rituximab, cyclophosphamide, epirubicin, vincristine, and prednisone (R-CHOP). Highly active anti-retroviral (HAART) therapy was started for HIV. After treatment with R-CHOP and HAART, the patient had complete resolution of the mass and symptoms on follow-up imaging and evaluation at 6 months.

CONCLUSIONS: Mediastinal DLBCL invading the heart is a life-threatening form of non-Hodgkin’s lymphoma (NHL) and early diagnosis and treatment is critical as prognosis is poor especially if diagnosed in later stages of the disease. Testing for HIV is important as 5% of HIV patients are susceptible to developing NHL.

Keywords: Lymphoma, AIDS-Related, Lymphoma, B-Cell, Lymphoma, Large B-Cell, Diffuse, Antineoplastic Combined Chemotherapy Protocols, Antiretroviral Therapy, Highly Active, Cough, Cyclophosphamide, Diagnosis, Differential, Dyspnea, Echocardiography, Transesophageal, Fatigue, HIV Infections, Heart Neoplasms, Mediastinal Neoplasms, Prednisone, rituximab, Tomography Scanners, X-Ray Computed, Vincristine, Weight Loss