Microscopic tumour embolism: an unusual cause of ventilation-perfusion mismatch

Microscopic tumour emboli are a rare complication of malignant disease. That they may cause multiple perfusion defects on radionuclide lung images without affecting ventilation is not widely recognized (Datz,1980). We report a case of such emboli causing ventilation-perfusion (V/Q) mismatch in a patient with no antecedent history of malignancy. A 59-year-old woman presented with a 5-month history of progressive exertional dyspnoea and intermittent pleuritic chest pain. There were no other respiratory symptoms and shehad never smoked. Systematic enquiry and past medical history were unremarkable. Examination showed her to be dyspnoeic at rest with a respiratory rate of 40/min, pulse of 100/min and blood pressure of 190/110 mmHg. A right ventricular heave was palpable, the jugular venous pressure was raised by 2 cm and bilateral pleural rubs could be heard. Achest radiograph was normal. Bipedal venography showed extensive bilateral deep vein thromboses and perfusion image susing technetium-99m-labelled albumen microspheres demonstrated multiple, small, peripheral defects throughout both lung fields (Fig. 1). The ventilation studies using krypton 81m showed a normal pattern (Fig. 2).