A middle-aged man is chronically preoccupied with his health. For many years he feared that his irregular bowel functions meant he had can-cer. Now he is very worried about having a serious heart disease, despite his physician’s assurance that the occasional “extra beats” he detects when he checks his pulse are completely benign. Which of the following is the most likely diagnosis?

A. Somatization disorder

B. Hypochondriasis

C. Delusional disorder

D. Pain disorder