The British Medical Journal Case Reports posted pictures of the pen inside the 76-year-old woman's stomach.
She was seeing a specialist for stomach-related problems when a doctor noticed the pen in a CT scan.
The woman said she had been poking her tonsils when she accidentally swallowed it in the mid-1980s.
The pen was removed from her stomach although doctors say it wasn't causing problems. Amazingly the felt-tip pen could still write after it was removed.
