S6467 Metastatic Gastric Glomus Tumor Presenting With Tumor Thrombus Extending to the Right Atrium: A Rare Gastrointestinal Case

Introduction: Gastric glomus tumors (GGTs) are rare mesenchymal neoplasms that are typically benign, with only a handful of cases progressing to metastasis. Malignant transformation and distant spread, especially with vascular invasion, are exceedingly rare and poorly understood. We present the first reported case of a metastatic gastric glomus tumor associated with tumor thrombus extending from the inferior vena cava (IVC) into the right atrium (RA). Case Description/Methods: A 75-year-old woman underwent excision of a gastric mass with partial gastrectomy in 2010 which was thought to be benign. In 2023, she presented with multiple new necrotic metastases throughout the liver and lung which was biopsy-proven to be metastatic GGT. Due to a new finding of tumor thrombus noted in the inferior vena cava (IVC) on computed tomography (CT) scan, a TTE was obtained that showed a right atrial mass (1.5 × 2.1 cm). A follow-up TEE with perfusion imaging showed immobile, lobulated, RA mass with heterogenous appearance (2.9 × 2.0 cm) extending from IVC to the IVC-RA junction. Perfusion imaging revealed the mass to be avascular. Discussion: Metastatic spread of GGT is rare, and tumor thrombus involving the IVC-RA junction has not been previously described. Given the patient's significant ascites, frailty, and risk of hemorrhagic or embolic complications, invasive intervention was deemed high-risk. The patient was managed conservatively with anticoagulation for thromboembolic prophylaxis. This case underscores the rare but aggressive behavior of gastric glomus tumors and highlights the importance of long-term surveillance in patients with previously resected GGTs. Gastrointestinal oncologists should maintain a high index of suspicion for vascular involvement in patients presenting with metastatic GGT. Multimodal imaging, including CT and echocardiography, plays a crucial role in detecting tumor thrombus and guiding management in complex gastroenterologic malignancies.