The single supratentorial lesion. An evaluation of preoperative diagnostic tests.

The role of preoperative diagnostic test was evaluated in 210 adult patients with single supratentorial lesions demonstrated by computerized tomography. At craniotomy, 59.5% of these patients proved to have primary brain tumors, 36.2% had metastatic tumors, and 4.3% had non-neoplastic lesions. In 23 (11%) of these patients, a single brain metastasis was the first manifestation of a systemic cancer. The primary site of cancer was identified in 14 patients (10 in the lung, three in the kidney, and one in the colon), and in nine patients the primary site could not be established. Using simple conditional probability theory, we established that the probability of a metastatic lesion in patients without a history of previously treated cancer is about 7%, if their chest x-ray film and intravenous pyelogram (IVP) are negative. Extensive preoperative testing to try to establish a primary site is unrewarding if the chest x-ray film and IVP are negative, since these are the only sites likely to be identified in these patients. In patients with a history of previously treated cancer, thest tests are justified because they have prognostic value in determining treatment.