Case Presentation: An 80 year old man presented to the hospital with progressively worsening dyspnea for three weeks. His past medical history was most significant for stage IV parotid gland adenocarcinoma. One week prior to presentation he was hospitalized for exertional dyspnea. Though the hypoxia workup at that time did not reveal a clear etiology, he was discharged with a new requirement of 4 liters of oxygen via nasal cannula.On this admission, the patient had worsened hypoxemia and now required FiO2 80-100% supplementation via high flow nasal cannula to maintain saturation above 90%. His exam was negative for volume overload or orthodeoxia. A CT angiogram showed multiple lung nodules, but did not reveal any pulmonary embolism or parenchymal disease that could explain the degree of hypoxia. Echocardiogram revealed a patent foramen ovale with right to left shunt (fill in findings). Empiric diuresis and high dose steroids did not improve his respiratory status.In order to evaluate the degree of shunting and hypoxia, a right heart catheterization was performed. Pulmonary wedge blood aspiration was collected during the procedure for cytologic evaluation, which returned positive for high grade carcinoma. The patient unfortunately decompensated after the procedure requiring intubation. After the diagnosis of tumor embolism syndrome was made, the patient was transitioned to comfort care, and he was palliatively extubated on hospital day 12.
Discussion: Pulmonary tumor embolism has been described in a wide variety of solid malignancies, most commonly urothelial carcinoma and invasive ductal carcinoma of the breast.1 Pulmonary tumor microembolism are not uncommon; an autopsy series on patients with solid malignancies found 26% had neoplastic emboli.2 However, they are a rare cause of hypoxemic respiratory failure or pulmonary arterial hypertension, since these require occlusion of a significant portion of the pulmonary vasculature. In the above series, occlusion of >30% of pulmonary arterioles occurred in only 6% of the patients with neoplastic emboli.2 In these symptomatic patients, respiratory symptoms developed an average of 14 months after diagnosis of malignancy, and often progressed rapidly with a mean of only one month between respiratory symptoms and death.3 Despite rapid progression, it is most frequently diagnosed post-mortem, often without ante-mortem consideration due to diagnostic difficulty.4 While macro-emboli may be visualized on CT angiogram, micro-emboli require lung biopsy or pulmonary wedge aspirate for diagnosis.5
Conclusions: While pulmonary tumor microembolism is a rare cause of severe progressive dyspnea, it remains an important diagnostic consideration in patients with known solid malignancies. While reduction of the underlying tumor burden through chemotherapy and radiation as well as respiratory supportive care are the mainstays of treatment, there are experimental anti-inflammatory and pulmonary vasodilation approaches being trialed.5 Early clinical suspicion and antemortem diagnosis, would allow prognostic clarity and consideration of all treatment options for patients with otherwise poor prognosis.