We report the case of a 49-year-old woman with a prior history of breast cancer who presented with a subacute course of progressive dyspnoea, culminating in cardiovascular collapse from acute right heart failure. D-dimer serum level was elevated. While a computed tomography of the chest was negative for pulmonary embolism, the autopsy study revealed multiple carcinomatous emboli in distal pulmonary arteries, veins, and lymphatics. Pulmonary tumor embolism may be more frequent than previously thought, and could be mistaken for pulmonary thrombo-embolism.