Visual loss from a pituitary mass: collision tumors of prostatic metastasis and suprasellar meningioma.

Central nervous system spread from prostate cancer is typically associated with raised prostate specific antigen (PSA) levels. The authors describe a unique case of a "collision tumor" of a prostatic metastasis to the pituitary, juxtaposed to a suprasellar meningioma, with normal PSA levels. This case also emphasizes the need to consider prostatic metastasis in the differential diagnosis of a pituitary mass in patients with a known prostatic cancer, despite the normal PSA levels.