Due to the proximity of the transvers sinus (TS) to the left atrial appendage (LAA) and pulmonary veins (PV), a mass in the TS can be misinterpreted as a LAA or PV thrombus, and considered as a source of emboli in a patient with stroke or transient ischemic attack. The incorrect identification of a mass as a LAA thrombus would initiate unnecessary anticoagulation therapy or potentially, an evaluation for the excision of the mass if there is a concern about dislodgement. We are presenting a case illustrating this confusion and review the literature for similar cases.