Infective Endocarditis due to Esophageal Squamous Cell Carcinoma Invasion of the Left Atrium: A Case Report

INTRODUCTION Esophageal cancer is often diagnosed at an advanced stage and with distant metastases. While cardiac metastases from solid tumors have been reported in 0.2%–6.5% of postmortem cases, solitary cardiac metastases remain exceedingly rare. Infective endocarditis, a life-threatening condition typically associated with valvular involvement and bacteremia, has not been widely associated with cardiac metastases. Here, we present an extremely rare case of esophageal squamous cell carcinoma directly invading the left atrium during chemotherapy, which was further complicated by infective endocarditis. CASE PRESENTATION A 52-year-old female who presented with chest and back pain and progressive dysphagia was diagnosed with esophageal squamous cell carcinoma following an endoscopic biopsy. Chemotherapy and chemoradiotherapy resulted in inadequate tumor control. During the second course of second-line chemoimmunotherapy, the patient developed a high fever, followed by seizures and loss of consciousness, and required emergency intubation. Echocardiography revealed a mobile mass 5 × 30 mm in size attached to the posterior wall of the left atrium. To prevent further embolic complications, emergency surgery was performed, which revealed a tumor invading the left atrial wall. Histopathological findings revealed a necrotic mass containing keratinizing squamous cell carcinoma fragments and a septic thrombus, consistent with infective endocarditis originating from the tumor surface. The patient did not regain consciousness following surgery, possibly because of hypoxic–ischemic brain injury following seizure-induced hypoxemia. Infection control remained poor, and the patient died of sepsis on POD 56. CONCLUSIONS Direct invasion of the left atrium by esophageal squamous cell carcinoma is rare, and infective endocarditis arising from tumor surfaces within the cardiac chamber is exceptionally uncommon, particularly in immunosuppressed patients. In this case, surgery was performed to prevent further embolic events and remove the infected tumor mass. Although the direct source of the infection was surgically removed, infection control remained difficult, likely due to persistent infection under immunosuppressive conditions and the use of cardiopulmonary bypass. This case highlights the challenges of managing infective endocarditis in patients with cancer and suggests that early surgical intervention may help reduce embolic risk, even when complete infection control cannot be achieved.