Primary breast lymphoma is a rare form of extranodal lymphoma. B cells constitute the most common type involving the breast. T cells represents only 3%. Even though lymphomas have a high predilection to metastasize to the heart, there are no specific clinical or radiological findings, and most of the cases are diagnosed at autopsy. We discuss the case of a 49-year-old woman with primary breast lymphoma who presented with sudden death. Autopsy revealed a primary T-cell lymphoma of the breast with tumoral infiltration of the atrioventricular node and transmural myocardial permeation with focal necrosis.