Small cell carcinoma presenting as a biatrial mass with obstructive physiology: a case report.

Background: Small cell carcinoma is a highly aggressive and often fatal cancer that most commonly arises in the lung, although it can occasionally arise from other sites, such as the gastrointestinal tract, prostate or cervix. Cardiac involvement, however, is extremely uncommon and therefore has been poorly documented in the literature.

Case Presentation: We describe a rare case of a 31-year-old male with small cell carcinoma presenting as a massive, 15-cm cardiac tumor invading the bilateral atria, interatrial septum, and pericardium without an apparent primary malignancy on PET CT and cardiac MRI. With extensive tissue necrosis, traditional methods of obtaining a right atrial endomyocardial biopsy via internal jugular venous access failed and a diagnosis was made via endoscopic ultrasound guided transesophageal fine needle aspiration of the left atrial mass. Due to the extensive tumor invasion, the patient was not a suitable candidate for surgical resection, debulking, or heart transplant. The patient was treated with etoposide, carboplatin, atezolizumab, and radiation therapy with initial monitoring in the intensive care unit due to concern that tumor lysis may cause rapid cardiac decompensation. Unfortunately, 4 months after chemoradiation therapy, the malignancy progressed and the patient passed away 6 months after the initial diagnosis.

Conclusion: We describe a rare occurrence of small cell carcinoma presenting as a massive cardiac tumor without apparent primary malignancy. This case demonstrates useful alternative diagnostic strategies and treatment considerations for patients presenting with a rare cardiac mass.