Background: Reversible schizophrenia-like syndromes have been reported to occur with small-cell carcinoma of the lung, thymoma, and hematological disorders.Case Report: A 56-year-old man was admitted due to an acute psychosis characterized by delusions, agitation,and aggressive outbursts. His medical and psychiatric history was unremarkable. On treatment with olanzapine, valproic acid, and perazine there was only moderate improvement. Extensive checkup revealed an isolated mediastinal metastasis of an undifferentiated carcinoma. A primary tumor was not found. After removal of the metastasis, the psychosis remitted rapidly and completely, and the patient remained well on follow-up.Conclusions: Paraneoplastic syndromes may clinically present as acute psychoses and, in late-onset schizophreniform disorders with an atypical presentation, performing a tumor search should always be considered.

Keywords: Mediastinal Neoplasms - secretion, Paraneoplastic Syndromes, Nervous System - drug therapy, Perazine - therapeutic use, Psychotic Disorders - etiology, Valproic Acid - therapeutic use, Antipsychotic Agents - therapeutic use, Benzodiazepines - therapeutic use, Mediastinal Neoplasms - surgery, Paraneoplastic Syndromes, Nervous System - etiology, Perazine - therapeutic use, Psychotic Disorders - etiology, Valproic Acid - therapeutic use