Abstract
Primary cardiac lymphoma is a rare, often fatal malignancy that can cause disorders of conduction depending on tumor location. We report two cases with sick sinus syndrome and atrial flutter secondary to primary cardiac lymphoma originating from the right atrium. One case required pacemaker implantation in the chronic phase after complete remission of lymphoma, and the other case in the acute phase when cardiac mass occupied the right atrium. Depending on the disease activity of lymphoma including its size, growth rate, and degree of invasion, the clinical course of sinus node dysfunction varies between each patient. In patients with conduction disorders, we suggest that long-term cardiac monitoring is necessary not only at onset but also after complete remission of lymphoma.