# Case Report: Unraveling a web of clots: marantic endocarditis as a paraneoplastic manifestation of lung cancer

## TL;DR

This case report describes a rare complication of lung cancer where blood clots form on heart valves, highlighting the importance of early detection and cancer treatment.

## Contribution

The case presents a rare combination of metastatic lung cancer and marantic endocarditis with multiple thrombotic events and successful treatment outcomes.

## Key findings

- The patient had metastatic EGFR-mutated lung adenocarcinoma complicated by marantic endocarditis and multiple embolic events.
- Anticoagulation and targeted EGFR therapy led to significant clinical and radiologic improvement, including resolution of the valvular lesion.

## Abstract

Marantic or non-bacterial thrombotic endocarditis (NBTE) is an uncommon but clinically important complication of malignancy, driven by a profound hypercoagulable state. It occurs most frequently in advanced adenocarcinomas and can present with a wide spectrum of thrombotic events, often mimicking infective endocarditis or other embolic disorders. We describe a rare presentation of metastatic EGFR-mutated lung adenocarcinoma complicated by NBTE, pulmonary embolism, splenic infarction, and acute coronary artery thrombosis. The diagnosis was supported by negative blood cultures, evidence of systemic emboli, and echocardiographic detection of a tricuspid valve vegetation. Management included prompt anticoagulation and initiation of targeted EGFR-directed therapy, which resulted in significant clinical and radiologic improvement, including complete resolution of the valvular lesion. This case underscores the need for heightened clinical suspicion for NBTE in patients with malignancy or unexplained embolic events, particularly when sterile valvular vegetations are identified. It also highlights the central role of effective cancer treatment—alongside anticoagulation—in reversing the prothrombotic state that drives NBTE.