Seventy two patients presenting with symptomatic brain metastases from undiagnosed primary neoplasms were retrospectively reviewed. Primary malignancies were diagnosed before death in 54 patients and remained unknown in 18 patients. Lung cancer was the most common primary tumour (72%), followed by breast cancer, colon carcinoma, and melanoma. On physical examination, 51 patients had organ specific symptoms or signs providing guidelines to the diagnostic evaluation. In 24 of the 52 patients with a primary lung tumour, and in four of the 20 patients without, organ specific complaints or findings suggested this tumour type, resulting in a positive predictive value of 85%.Overall, radiography and CT of the chest were very useful in detection of primary lung tumours. This could partly be explained by the high prior probability of detecting such tumours. Other diagnostic procedures should be used on indication only. The prognosis of patients with confirmed primary tumour position did not differ from those with unidentified primary tumour.

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