Incidental diagnosis of tricuspid marantic endocarditis in a patient with lung adenocarcinoma: a case report and review of the literature of an underrecognized paraneoplastic manifestation of hypercoagulability

Nonbacterial thrombotic endocarditis (NBTE) is a rare condition potentially associated with malignancy-related hypercoagulability, typically affecting left-sided valves. Isolated tricuspid involvement is exceptional and may be incidentally diagnosed in the setting of pulmonary embolism. The therapeutic management of NBTE primarily relies on anticoagulation. We report a rapidly progressive case of tricuspid NBTE revealed by thromboembolic events in a 48-year-old man with unresectable lung adenocarcinoma treated with chemoimmunotherapy. Echocardiography initially identified a small tricuspid valve mass that demonstrated rapid growth despite anticoagulation, increasing from 8×3 mm to 37×13 mm within 3 weeks. The lesion was highly mobile and heterogeneous, without valvular dysfunction. Due to the risk of embolization, surgical excision was performed with preservation of the native valve. Histopathology confirmed NBTE, showing sterile fibrin–platelet vegetations with focal calcifications. In the context of malignancy-associated hypercoagulability, this case highlights the importance of regular echocardiographic assessment of cardiac valves in patients with predisposing risk factors for NBTE to reduce the risk of acute adverse events. Rapid progression of a valvular mass despite adequate anticoagulation should prompt consideration of surgery to prevent embolic complications.