A63-16 Yolk Sac Tumor Associated Pulmonary Tumor Thrombotic Microangiopathy: A Novel, Occult, and Fatal Cause of Rapidly Progressive Pulmonary Hypertension

Abstract Pulmonary emboli (PE) affect approximately 60-120 individuals per 100,000 annually, with most cases (88-90%) being thrombotic. Pulmonary tumor emboli (PTE), defined as pulmonary arterial occlusion by cohesive tumor cells without parenchymal metastases, are far less common, with autopsy-based incidence ranging from 0.2-2.3% in cancer patients. Pulmonary tumor thrombotic microangiopathy (PTTM) is a distinct and often fatal subset of PTE in which microscopic tumor emboli induce fibrocellular intimal proliferation and progressive pulmonary hypertension, leading to right-sided heart failure and sudden death. PTTM is classically associated with gastric adenocarcinoma, with only isolated reports in other solid tumors. Germ cell tumors (GCTs) in adult women, including yolk sac tumors (YSTs), are exceedingly rare and their association with PTTM has not been previously described. A 43-year-old woman with past medical history significant for iron-deficiency anemia, confluent and reticulated papillomatosis, presented to our hospital with one month of progressive exertional dyspnea and tongue cyanosis. On admission, her vitals were notable for tachycardia and hypoxia. CT Angiogram of the chest revealed no thrombotic emboli, while transthoracic echocardiogram demonstrated moderate right ventricular dilation, elevated right ventricular systolic pressure, and patent foramen ovale (PFO) with right-to-left shunting consistent with Eisenmenger physiology. Ventilation-perfusion scanning showed multiple mismatched perfusion defects concerning for nonthrombotic embolic or stenotic disease. Lower extremity duplex ultrasounds were negative for clots. Laboratory testing, including ANCA and D-dimer, were unrevealing. Despite the initiation of prostacyclin therapy, the patient’s respiratory failure rapidly progressed, and she expired from a cardiac arrest on hospital day 10. Post-Mortem autopsy revealed diffuse intravascular tumor emboli involving all lung lobes, with fibrointimal proliferation consistent with PTTM. Immunohistochemistry was positive for CK7, CK20, PLAP, AFP, and HCG, and negative for OCT-4 and CD30, consistent with a yolk sac tumor of extragonadal origin. No primary gonadal lesion had been identified. This case represents, to our knowledge, the first reported instance of PTTM secondary to a yolk sac tumor. It highlights the diagnostic challenge of nonthrombotic causes of pulmonary hypertension, particularly in patients with unexplained right heart strain and hypoxemia without imaging evidence of thrombotic PE. Recognition of PTTM as a potential etiology is crucial, as early suspicion and multidisciplinary evaluation may facilitate earlier diagnosis and targeted therapy in select cases. This abstract is funded by: None