Rare Acute Presentation of a Low-Grade Thymic Neuroendocrine Tumor.

Primary neuroendocrine tumor (NET) of the thymus is very rare. Here we report an unusual presentation of grade-I typical thymic NET in a 63-year-old female who presented with signs and symptoms of congestive heart failure (CHF) due to the mass effect from the huge tumor. A computed tomography (CT) scan of the chest revealed a mediastinal mass measuring 16.4 x 12 x 15.3 cm displacing most of the left lung parenchyma, with mass effect on the heart, and encasing the ascending aorta and main pulmonary trunk. Pathology report from the thymic mass biopsy showed tumor cells strongly expressing synaptophysin, chromogranin A, and cluster of differentiation (CD)56 markers. The diagnosis was consistent with grade-I typical thymic NET based on low Ki-67 and morphology. The patient was not in agreement for acute surgery or oncological treatment options. Thus, the plan was made to embolize the arteries from the right coronary artery that were feeding the mass in an effort to shrink the size with goals of future surgical resection. However, given the advanced stage of the diagnosis with mass effect on the heart and the patient's reluctance to consider the main definitive treatment options, the prognosis was extremely poor and the patient eventually passed away.