Metastatic breast carcinoma presenting as a large pulmonary embolus: case report and review of the literature.

Involvement of the pulmonary vasculature by carcinoma of the breast typically occurs in the form of microscopic tumor emboli involving the small arteries, arterioles, or capillaries. Obstruction of a large pulmonary artery by a tumor embolus has not been reported. We describe a patient with a history of breast carcinoma diagnosed 5 years previously who sought treatment for dyspnea and a large mass in the right pulmonary artery suggestive of a pulmonary embolus. After failure of both systemic and intraarterial thrombolytic therapy, a biopsy of the mass was obtained, which revealed adenocarcinoma of the breast. Systemic chemotherapy with doxorubicin and cyclophosphamide was initiated and resulted in the complete resolution of her symptoms.