The diagnosis of primary cardiac lymphoma was facilitated by computed tomographic coronary angiography.

Primary cardiac lymphoma (PCL) is a rare entity that leads to fatal symptoms such as serious arrhythmia. The present case was an 80-year-old female with severe dyspnea caused by 30 bpm bradycardia. Computed tomography revealed a tumor invading to the right inferior myocardium. A computed tomographic coronary angiography (CTCA) study revealed the right coronary artery penetrating the tumor with no invasion by the surrounding tumor. Because a percutaneous biopsy was unsuccessful, video-assisted thoracic surgery (VATS) was performed. The final pathological diagnosis was diffuse large B cell lymphoma. Rituximab plus cyclophosphamide, doxorubicin, vincristine, and prednisolone (R-CHOP) chemotherapy reduced the size of the tumor, and the symptoms thereafter improved. An observation of the coronary artery penetrating the tumor without tumor invasion may be a characteristic finding of PCL. CTCA is useful to detect this finding. When a percutaneous biopsy is unavailable, VATS should be considered as a minimally invasive procedure to obtain a reliable diagnosis of PCL.