A 35 year old man feels that he is about to die because he is suffering from gastric cancer. All his radiological investigations prove the contrary. Which is the most probable diagnosis?

Hypochondriasis (Illness anxiety disorder - DSM-5) Severe persistent anxiety about ill health and conviction of disease, with repeated presentation of concern about the possibility of one or more specific diseases (such as cancer, hea disease), despite negative medical investigations and appropriate reassurance. Somatic symptom disorder: Person is more concerned about the symptoms than the diagnosis. Delusional disorder: Despite all the evidences against it the belief is firm, fixed and unshakable.