Incidental detection of a probable metastatic right ventricular outflow tract mass with right ventricular free wall involvement from gastric adenocarcinoma: a multimodality imaging case report.

Background: Probable metastatic cardiac involvement from gastric adenocarcinoma may rarely present as a clinically silent right-sided cardiac mass involving the right ventricular outflow tract (RVOT) and right ventricular free wall. Case Summary: A 60-year-old man with newly diagnosed metastatic gastric adenocarcinoma underwent baseline cardio-oncology assessment prior to chemotherapy. Transthoracic echocardiography revealed a large heterogeneous RVOT mass (3.1 × 2.0 cm) with preserved left ventricular systolic function (LVEF 50-55%) and no significant obstruction (peak gradient 16 mmHg). Transoesophageal and three-dimensional echocardiography demonstrated a sessile, non-pedunculated lesion with broad-based attachment. Cardiac magnetic resonance imaging showed an infiltrative mass with heterogeneous late gadolinium enhancement, with imaging features highly suggestive of metastatic involvement. A catheter-associated thrombus served as an internal comparator. The patient remained asymptomatic and proceeded to systemic therapy. Discussion: This case illustrates an uncommon pattern of probable metastatic cardiac involvement presenting as a right-sided cardiac mass involving the RVOT and right ventricular free wall, detected incidentally in an asymptomatic patient. It further shows that baseline cardio-oncology imaging, performed for pre-treatment cardiovascular assessment, may incidentally identify clinically relevant structural abnormalities. Multimodality imaging supported characterization of the lesion and helped guide management.