Tumor cell embolism to pulmonary alveolar capillaries. Cause of sudden cor pulmonale.

A 51-year-old woman, with a 13-month history of widely metastatic breast carcinoma treated with radical mastectomy and chemotherapy, developed sudden shortness of breath and chest pain. Rapidly progressive pulmonary hypertension was documented that failed to respond to supportive measures, and the patient died. The lungs at autopsy demonstrated tumor microemboli in the form of noncohesive, individual cells within the capillaries of approximately 40% of the pulmonary alveolar septae. This case is remarkable for widespread involvement of the alveolar septal capillaries as the cause of acute cor pulmonale.