Pulmonary Tumor Thrombotic Microangiopathy Diagnosed by Right Heart Catheterization in a Patient With Breast Cancer: A Case Report

Pulmonary tumor thrombotic microangiopathy (PTTM) is a severe complication of malignancy, characterized by rapidly progressive pulmonary hypertension and a dismal prognosis. This report describes the case of a 71-year-old woman with a history of estrogen receptor (ER)-positive left breast cancer who developed PTTM. She presented with exertional dyspnea and a cough. Arterial blood gas analysis revealed hypoxemia with an elevated alveolar-arterial oxygen gradient. Chest computed tomography (CT) showed diffuse ground-glass and nodular opacities without obvious pulmonary embolism (PE). Echocardiography revealed right ventricular enlargement and moderate pulmonary hypertension. Right heart catheterization confirmed severe pulmonary hypertension with a mean pulmonary artery pressure of 46 mmHg and pulmonary vascular resistance of 844 dynes/sec/cm⁵. After transbronchial lung biopsy (TBLB) and bronchoalveolar lavage (BAL) failed to yield a diagnosis, PTTM was confirmed by detecting malignant cells via cytology of blood aspirated from the pulmonary artery during catheterization. The administration of systemic chemotherapy resulted in a marked improvement in hemodynamics, radiological findings, and symptoms, allowing her to be weaned from home oxygen therapy.