1357806 - Rare case of neuroendocrine tumor metastasis in the right ventricular wall

We present the case of a 68-year woman with a long history of abdominal pain and recurrent bouts of partial small bowel obstruction. She was initially diagnosed with Crohn's disease and presented with progressing weight loss.

Diagnostic Techniques and Their Most Important Findings:

A contrast-enhanced CT chest/abdomen/pelvis was performed demonstrating a hypervascular mass in the terminal ileum/ileocecal valve resulting in mild proximal small bowel dilatation (Fig 1A). Furthermore, a small lesion in the lateral right ventricular (RV) free wall was detected (Fig 1B). Workup for a neuroendocrine tumor (NET) was performed with 68Ga-DOTATATE PET-CT which showed intense somatostatin receptor 2 (SSTR-2) uptake in the terminal ileum and a small RV wall lesion (SUV_max 18) (Fig 1 C and D). Patient underwent 3T cardiac MRI (CMR) for tissue characterization of the RV wall lesion. The lesion measured 9x8 mm (Fig 2 A to F). Signal characteristics compared to myocardium were as follows: hyperintense on T2-STIR, hypointense on T1-TSE without FS pre-GBCA, hyperintense on T1-TSE with FS after GBCA, central mild nodular LGE focus. The patient underwent surgery and histopathology revealed with a well differentiated NET grade 1 involving the distal ileum and cecum.

Learning Points from this Case:

NETs are a heterogeneous group of tumors that develop from neuroendocrine cells, most commonly the gastrointestinal tract, lungs, or bronchi (1). Metastatic disease mostly involves the liver, but can involve bones, lungs or peritoneum (2). Cardiac metastases are rare (~4%) and are generally detected incidentally (3,4), with clinical presentation varying from asymptomatic to carcinoid heart disease (2).

68Ga-DOTATATE PET-CT imaging has improved the detection of metabolic active metastases from NETs. However, CMR has the unique ability for non-invasive myocardial tissue characterization (e.g. T1/T2 mapping, T2 imaging, LGE) and therefore helps in differentiation of cardiac tumors. Differential diagnosis includes primary cardiac tumors, metastasis from e.g. melanoma, NET, lymphoma infiltration or thrombus. Melanoma metastasis could be hyperintense on T1w and hypointense on T2w images.  Cardiac thrombus may vary in T1/T2 signal depending on age and calcifications have mostly low signal intensity on T1/T2w images. Cardiac NET metastases have an almost similar involvement of the RV (40%) and LV (53%). The interventricular septum is involved in 7% but may show diffuse myocardial infiltration (5). T1w imaging pre-GBCA and mapping may help differentiate cardiac thrombus from other tumor entities. In this case, thrombus, fat, melanin or calcification components were excluded, because those entities have short T1 relaxation times. On T2-STIR images the lesion is mildly hyperintense to myocardium and after GBCA there is mild enhancement similar to myocardium on T1w with FS noted, and a small central nodular LGE focus, in keeping with metastasis.

CMR should be considered in every patient undergoing staging for NET for further characterization of incidental cardiac tumors.