Case report
A 37-year-old male with a past medical history of hypothyroidy presented to the emergency department with complaints of progressive exertional dyspnea (NYHA class II-III), anorexia and epigastric pain for a couple of days. The laboratory test results were unremarkable. Transthoracic echocardiogram (TTE) and transesophageal echocardiogram (TEE) revealed the presence of a left atrial mass of 40 X 26 mm originating from the interatrial septum and causing a dynamic obstruction of the mitral valve. The mass was attached by a narrow pedicle of 4 mm localized on the interatrial septum between the fossa ovalis and the insertion of the anterior mitral leaflet (Fig. 1). Cardiac magnetic resonance imaging (MRI) confirmed the presence of a homogeneous atrial mass with isosignal intensity on T1-weighted images and increased T2 signal, without contrast enhancement after Gadolinium injection (Fig. 2).The most likely diagnosis for this mass was a large myxoma and the patient was scheduled for a surgical resection without delay.
Surgery was performed under a minimally invasive thoracoscopic approach (small incision in the right 4th intercostal space, 2 percutaneous venous cannulas respectively inserted in the right internal jugular vein and in the right femoral vein). A transseptal approach via the right atrium was preferred in order to resect part of the interatrial septum if needed. After incision of the interatrial septum, we discovered a reddish, slightly gelatinous mass, attached to the lower part of the interatrial septum by a small pedicle (Fig. 3). The pedicle was resected with a small patch of the interatrial septum and the mass was removed. The interatrial septum was closed directly without interposition of a patch. Postoperative course was uneventful. Gross pathology of the operative specimen showed an encapsulated mass of 4.3 X 3.2 X 2.4 cm with soft consistency. Microscopic examination revealed the presence of a myxoid matrix with some cellular zone, in which spindle or stellar cells are identified (Fig. 4). Some nuclear atypias were present, however without abnormal mitotic figures. On this basis, pathologic analysis confirmed the diagnosis of cardiac myxoma. Patient was discharged from the hospital by day 7. One month after hospital discharge, the patient was rehospitalized for bronchopneumonia and atrial fibrillation (AF). The cardiac imaging by TTE and thoracic CT performed at this time did not show any evidence of cardiac mass recurrence. Patient was treated by antibiotics and antiarrhythmic drugs with favorable clinical course. Four months after surgery, patient experienced recurrent AF and the routine TTE showed a recurrence of a left atrial mass of 26 X21 mm, with irregular shapes. TEE and cardiac MRI confirmed the features of the mass that is attached to the atrial septum at the same place as the previous tumor (Fig. 5). Although the recurrence occurred early, the presumptive diagnosis at this moment was a recurrent left atrial myxoma. A surgical resection of this recurrent left atrial mass was performed under median sternotomy and cardiopulmonary bypass. Due to recent history of paroxysmal AF, a concomitant surgical AF ablation procedure (Cox-Maze 4) was performed in the same operative time. A yellowish, slightly lobulated mass was removed, excising part of the interatrial septum (Fig. 6). The defect in the atrial septum was closed using a pericardial patch. Macroscopic examination of the specimen demonstrated a mass of soft consistency measuring 3.2 X 3 X 2.6 cm. Histology showed an edematous stromal tissue with area of moderate to high cellularity. In these areas, packed spindle cells and stellar cells are found with fascicular growth pattern. The tumor cells had pleiomorphic, polylobed nuclei with frequent abnormal mitotic figures. Immunohistochemical analysis revealed an intense expression of the MDM2 oncogene in tumor cell nuclei, confirming the diagnosis of intimal sarcoma (Fig. 7). Adjacent atrial septum and resection margins were free of tumor. Early postoperative evolution was favorable and patient was discharged home by day 9. An adjuvant chemotherapy with doxyrubicin was administered for a total of 6 cycles. A metastasis in the left adrenal gland was discovered on the PET-CT at 1-year follow-up. Patient underwent a successful surgical resection of this metastasis and pathology confirm that it was a metastasis of the intimal sarcoma. An additional adjuvant chemotherapy with ifosfamide was given for 6 cycles and the patient is still in complete remission 18 months after the first operation.