Incidental Right Atrial Thrombus in a Patient with Metastatic Pancreatic Neuroendocrine Tumor and Secondary Erythrocytosis

Moultrie, GA

Introduction Pancreatic neuroendocrine tumors (pNETs) are rare neoplasms arising from the endocrine cells of the pancreas and represent a small subset of pancreatic malignancies. Although they often follow an indolent clinical course, pNETs have a known propensity for metastatic spread, most commonly to the liver. Vascular invasion and tumor thrombus formation are uncommon but clinically significant complications that may result in life-threatening cardiopulmonary sequelae. We present a case of a 60-year-old male with a history of pancreatic tail neuroendocrine tumor status post distal pancreatectomy and splenectomy, complicated by hepatic metastases and an incidental large right atrial thrombus identified on transthoracic echocardiography.

Methods This case report was prepared using retrospective review of the patient’s electronic medical record, imaging studies, laboratory data, and multidisciplinary consultation notes in accordance with CARE (CAse REport) guidelines. Imaging included contrast-enhanced computed tomography (CT), magnetic resonance imaging (MRI), transthoracic echocardiography (TTE), and transesophageal echocardiography (TEE) to evaluate intra-abdominal disease burden and intracardiac pathology. Identifying information was omitted to preserve patient confidentiality.

Results A 60-year-old male with a history of pancreatic tail neuroendocrine tumor status post distal pancreatectomy and splenectomy with known hepatic metastases presented with one day of bright red blood per rectum and lightheadedness upon standing. Past medical history included type 2 diabetes mellitus, obstructive sleep apnea, hemorrhoids, secondary polycythemia, and an indwelling permanent pacemaker. Orthostatic vital signs were positive. Laboratory evaluation demonstrated no acute anemia (hemoglobin 17 g/dL). A comprehensive metabolic panel showed a high anion gap metabolic acidosis with elevated lactate (3.48 mmol/L), improving to 2.78 mmol/L after intravenous fluid resuscitation, with significant symptomatic improvement. Fecal occult blood testing was negative.

Computed tomography of the abdomen and pelvis demonstrated no acute intra-abdominal pathology or active gastrointestinal bleeding. Multiple hypoattenuating hepatic lesions were visualized, consistent with known metastatic disease. Given presyncope in the setting of reported hematochezia, the patient was admitted for overnight monitoring of hemodynamic stability and recurrent orthostatic symptoms.

Transthoracic echocardiography revealed two mobile right atrial structures. Subsequent transesophageal echocardiography further characterized the structures as a 1.4 × 1.4 cm bilobed mass adherent to the right atrial wall, concerning thrombus. Due to embolic risk, the patient was transferred to Mayo Clinic for cardiothoracic surgical management. Outside records were unavailable; however, the patient reported successful intervention and resolution of symptoms.

Discussion This case illustrates the multifactorial thrombotic risk associated with active malignancy, compounded by secondary erythrocytosis and prior splenectomy. Malignancy-related hypercoagulability and elevated hematocrit likely contributed to thrombus formation. Although the thrombus was not associated with the pacemaker lead, the presence of a transvenous device may alter atrial flow dynamics and promote endothelial injury, further increasing risk in predisposed patients. Negative mutation testing supported secondary polycythemia rather than a myeloproliferative neoplasm, emphasizing the role of acquired prothrombotic factors. Clinically, intracardiac thrombosis should be considered in high-risk patients presenting with syncope or unexplained symptoms, and early echocardiography can enable timely, potentially life-saving intervention.