A Man in His 40s With Headache, Lethargy, and Altered Mental Status.

A man in his 40s presented with 1 month of worsening confusion, fatigue, and headache. Results from laboratory analyses were notable for a complete white blood cell count of 17 000/μL (31% blast cells), a platelet count of 76 000/μL, and a hemoglobin level of 16.6 g/dL. Imaging studies revealed a large mixed-attenuation subdural collection in the right frontal region with prominent mass effect. The patient underwent an emergency neurosurgical procedure. The differential diagnosis, pathologic findings, and diagnosis are discussed.