The patient in the question presents with anxiety about having a paicular diagnosis like a tumour. He is not convinced by the evidence against it. He has a belief that he has a life threatening diagnosis. This is indicative of Hypochondriasis. Hypochondriasis can be a severe anxiety or in worse cases Delusional Hypochondriasis which can be considered as psychosis. In somatisation disorder the patient is often worries about multiple symptoms, not a paicular diagnosis. Pituaitary tumour could present with a bitemporal hemianopia. Capgras syndrome is a misidentification delusion.