A. teratoma.

A 62-year-old man complained of headaches for the last 5-6 months. Lately the pain had become intolerable. He was vomiting frequently, and complained of decreased visual acuity. Physical examination revealed the presence of papilledema. Spinal tap showed increased spinal fluid pressure (280 mm of water; normal 100-200) with a normal sugar level but increased protein content (120 mg/100 ml; normal 15-40). Following an NMR scan, craniotomy was performed and this specimen was removed.

Based on the location and histology this tumor is best classified as...