Abstract: Objective To define the clinicopathological features of primary cardiac large B-cell lymphoma. Method A case of primary cardiac large B-cell lymphoma was studied with conventional histopathological and immunohistochemical staining in combination with literature review. Results The lesion appeared to originate in the right atrium and involved the venae cavae and the left atrium. Microscopic examination showed diffuse proliferation of large atypical lymphocytes with abundant cytoplasm, vestiealer nuelei, thick nuclear membrane and conspicuous nucleoli. Giant tumor cells scattered in the lesion. The neoplastic cells were positive for CD20 and CD79a. Conclusion Primary cardiac lymphoma is extremely rare, and its pathogenesis remains unclear. With non-specific clinical manifestations, the majority of primary cardiac lymphomas are of B-cell lineage and a bad prognosis..