Australian doctors mistook 15-year-old tattoo pigment for cancer in a case recently reported on in the Annals of Internal Medicine. This comes shortly after a paper published in the British Medical Journal, which describes the case of a British man whose "tumor" was actually a PlayMobil piece.

The incident started when a 30-year-old woman visited doctors concerned about some small lumps that had appeared on her underarms two weeks earlier. The medics soon diagnosed her with lymphoma – a type of cancer that develops in the lymphocytes (infection-fighting cells found in the immune system) and causes the lymph nodes to swell.    

A full-body scan showed additional enlarged lymph nodes in the chest, some of which had developed close to the roots of her lungs. But when the doctors examined one of these inflamed lymph nodes using a microscope, they realized it wasn't cancer. It turned out black tattoo pigment was the cause of the swelling.

Cancer is by far the most common reason for lymph nodes to enlarge, but infection can also cause inflammation. In this particular case, the lymph nodes had swollen because of a reaction to the old tattoo ink.

"Ninety-nine times out of 100, (this) will be lymphoma," Dr Christian Bryant explained, reports CNN. Bryant, a hematologist at the Royal Prince Alfred Hospital in Sydney, treated the patient.

The woman had two tattoos: one on her back, completed 15 years ago, and a smaller, more recent one on her shoulder. Both were done using black ink.

Doctors suspect the swelling occurred because immune cells in the skin ingested the tattoo pigment. They would have been unable to digest it properly, however, as the particles are too large. Years later, the pigment traveled from the skin to the lymph nodes. 

Still, what triggered the reaction 15 years after she got her first tattoo is unclear. 

Besides the bumps, the patient didn't notice many symptoms. She did tell doctors her tattoos would itch for a few days each month, but that the feeling would soon subside. 

The doctors involved say they haven't seen a case like it. "I think there's absolutely no way to know how common it is," said Bryant, according to CNN. "Most people who have tattoos have absolutely no problems."

Fortunately, the woman is doing well and her lymph nodes have returned to a normal size.

"It's not going to cause this lady any major problems," Bryant told CNN, "which means we're allowed to be interested without feeling sad."

"My job's often not like that."

Once upon a time, tattoos might have been edgy. Now, they're everywhere. Roughly three in 10 Americans sport at least one, and almost half of all millenials have gotten a tattoo, according to The Harris Poll.

As well as being certain you go to a reputable artist, don't forget to let your physicians know your tattoo history because, although rare, complications can happen.

[H/T: CNN]