Sterile Vegetations in Malignancy: A Rare Case of Nonbacterial Thrombotic Endocarditis in a Patient with Metastatic Melanoma.

Background and Clinical Significance: Nonbacterial thrombotic endocarditis (NBTE) is a sterile fibrin-platelet valvular condition associated with malignancy and hypercoagulable states. It produces friable vegetations prone to systemic embolization, often presenting as multifocal ischemic stroke. While modestly linked to advanced adenocarcinomas, its association with melanoma is exceedingly rare; Case Presentation: We present a 43-year-old man with recently diagnosed metastatic melanoma who presented with fever, confusion and abdominal pain. Brain magnetic resonance imaging (MRI) revealed multifocal bilateral acute infarcts. Additional imaging demonstrated splenic and bilateral renal infarcts. Transesophageal echocardiography (TEE) revealed an 8 mm × 7 mm multilobar lesion on the posterior mitral valve leaflet. Blood cultures remained persistently negative; autoimmune and infectious workup were unrevealing, and positron emission tomography-computed tomography (PET-CT) showed no cardiac hypermetabolism. Despite empiric antibiotics for suspected infective endocarditis (IE), progressive embolic infarcts occurred. After exclusion of infection, NBTE was considered, and therapeutic enoxaparin was initiated, resulting in clinical stabilization without hemorrhagic conversion; Conclusions: Distinguishing NBTE from IE remains challenging due to overlapping and nonspecific imaging findings. TEE is the preferred diagnostic modality because of its high sensitivity for detecting small valvular vegetations. Adjunctive imaging modalities such as brain MRI and PET-CT may support the diagnosis by demonstrating embolic patterns or excluding metabolically active infectious vegetations. Management primarily relies on systemic anticoagulation, while percutaneous vegetation aspiration may represent a potential diagnostic and therapeutic strategy. Clinicians should maintain high suspicion of this condition in patients with advanced melanoma and other malignancies presenting with multifocal embolic phenomena and negative cultures to enable timely anticoagulation.