Abstract
Pulmonary tumor thrombotic microangiopathy (PTTM) is a rare but serious complication that can occur in patients with advanced cancer. It often leads to rapidly worsening respiratory failure and right heart failure and is typically diagnosed only postmortem. While PTTM has been reported in various cancers, it is extremely rare in male patients with breast cancer, which is itself an uncommon malignancy. We report the case of a man with hormone receptor-positive breast cancer who underwent surgery followed by adjuvant chemotherapy. Several months later, he developed progressive dyspnea and increased levels of tumor markers. Although contrast-enhanced computed tomography (CT) scans revealed no evidence of pulmonary thromboembolism, the patient's right heart failure rapidly worsened, and he died shortly after hospital admission. Autopsy revealed classic histopathological features of PTTM, including tumor emboli and fibrous intimal thickening in the pulmonary arteries. To our knowledge, this is the first English-language report of PTTM arising from male breast cancer. This case highlights the importance of considering PTTM in patients with rare malignancies such as male breast cancer, particularly when they present with unexplained respiratory deterioration and signs of pulmonary hypertension. Early clinical suspicion may help guide timely therapeutic decisions.