A CT scan, published in BMJ, shows a pen lodged in an elderly woman's stomach.

The pen is mightier than the sword, so the saying goes. But in the case of an elderly British woman, a pen is also mightier than one's stomach acid.

An unidentified 76-year-old woman had a pen stuck inside her stomach for the past 25 years, according to a report in the British Medical Journal. Doctors at a hospital in Exeter found the pen on a CT scan when the patient came to the hospital complaining of weight loss and diarrhea.

The patient told her doctors that 25 years ago, she was using the pen to inspect a spot on her tonsils when she slipped, fell and accidentally swallowed the pen. Her physician husband didn't believe her story but took an x-ray of her stomach, which showed nothing inside of her.

So the pen remained in her stomach for over two decades, causing the woman no symptoms at all.

"The stomach does not have an extensive sensory innervation and the felt tip pen was blunt," Dr. Oliver Waters, a gastroenterologist who treated the woman, told ABC News. "So if the pen was not damaging the stomach this would explain the patient's lack of symptoms."

When Waters and his colleagues fished the pen out of its gastrointestinal hiding place, they found that it still wrote clearly.

"Normally the stomach acid will disintegrate things like the inside of a pen," Dr. Steven Moss, a gastroenterologist at Rhode Island Hospital, told ABC News. "For the tip to be still intact with ink after 25 years is amazing."

Doctors say the patient is probably lucky she chose a felt-tip pen to probe her tonsils.  Something sharper, such as a ballpoint pen, could have cut into the lining of her stomach and allowed the gut's bacteria to seep into the rest of her body. On the other hand, a ballpoint pen might have been easier for doctors to detect from the start.

"In all likelihood the pen didn't show up on the first x-ray because there are no metal pieces in a felt-tip pen," Dr. Michael West, a trauma surgeon at San Francisco General Hospital, told ABC News. "A ballpoint pen has several metal parts, like the springs and the tip, and would have been seen on an x-ray."

It's not uncommon for people to get objects stuck inside their bodies , but usually the objects either make their way through the stomach and intestines and emerge, or they make patients uncomfortable enough to seek medical help. Dr. Gary Vilke, an emergency physician at the University of California, San Diego Medical Center, said he sees many patients who have swallowed objects that remain inside for up to a week.

"But I've never seen something stay in there for so long," he said. "The pen must have just been moving around, bouncing around inside her stomach for 25 years. That's pretty unheard of."