Thrombus or Vegetation: A Diagnostic Dilemma in Cardiac Imaging.

Cardiac masses identified on echocardiography can pose significant diagnostic challenges, particularly when differentiating between thrombi and vegetations, which require markedly different management approaches. We present the case of a 57-year-old postmenopausal woman with a history of thymic cancer and recent pulmonary embolism (PE), who presented with abdominal pain, weight loss, and laboratory findings consistent with disseminated intravascular coagulation (DIC). Abdominal ultrasound and magnetic resonance imaging (MRI) revealed a large fibroid uterus with multiple masses concerning for leiomyosarcoma or leiomyoma, and transthoracic echocardiography (TTE) showed a large echo density on the tricuspid valve and a bicuspid aortic valve with mild-to-moderate stenosis. Further evaluation with transesophageal echocardiography (TEE) confirmed a large mass on the tricuspid valve and also revealed multiple echo densities on the mitral and aortic valves. Cardiac MRI (CMR) demonstrated thickened, mobile tricuspid valve leaflets with moderate regurgitation; mild-to-moderate mitral regurgitation was also seen, along with thickening of the mitral valve leaflets. However, the nature of the masses remained unclear. Despite negative blood cultures, the clinical and imaging findings raised suspicion for non-bacterial thrombotic endocarditis (NBTE), though thrombi remained a differential consideration. Given the patient's hypercoagulable state, a multidisciplinary team initiated anticoagulation and arranged close outpatient follow-up. A cervical lymph node biopsy subsequently confirmed metastatic, poorly differentiated carcinoma with immunohistochemistry positive for CKAE1/AE3, HMWCK, and PAX8, suggesting either recurrent thymic malignancy or a primary uterine origin. A few months later, repeat TTE showed reduced severity of mitral and tricuspid regurgitation, and the valvular masses were less apparent. The patient is currently undergoing palliative chemotherapy with carboplatin, paclitaxel, and dostarlimab, continues on lifelong anticoagulation, and receives comprehensive pain management. This case underscores the diagnostic complexity of cardiac masses, particularly in patients with malignancy. It highlights the critical role that multimodality imaging plays in resolving complex diagnostic dilemmas and emphasizes the importance of a collaborative approach in managing such patients.