A 63-year-old man complains of worsening headache and right-sided weakness. CT of the head is shown below. The most likely diagnosis is:

Ans. B. Brain tumor* The CT scan that accompanies the question reveals near the left cortex a solitary, rounded, discrete lesion that enhances with contrast and has mild surrounding edema. The history, examination, and CT scan suggest a brain tumor, either primary or metastatic.* Further work-up should be aimed at uncovering an occult primary tumor, if any. Common sources occur at the lungs, kidneys, colon, and breasts.* Chest roentgenogram, intravenous pyelography, gastrointestinal series, or mammography might therefore be indicated. A myelogram or lymphangiogram would not be helpful for most patients.* If an occult primary tumor cannot be found, biopsy of the brain lesion may be indicated.