“Ninety-nine times out of 100, [this] will be lymphoma,” one of the woman's doctors, Christian Bryant, told CNN.

But when surgeons removed one of the enlarged nodes from the woman's armpit, they discovered something else entirely — a collection of immune cells that were filled with dark coloring.

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The diagnosis? It was not cancer.

In a case report published in the Annals of Internal Medicine, the authors wrote that the 30-year-old woman, who was not identified, most likely had a hypersensitive reaction to ink from tattoos.

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The authors wrote in their findings that tattoos can be linked to “acute complications, such as pain, infection and hypersensitivity” as well as enlarged lymph nodes that may “masquerade as malignant disease.”

The U.S. Food and Drug Administration says it received 363 reports about adverse reactions to tattoos from 2004 to 2016.

Granted, that's a small number of those who get tattoos in the United States: A 2015 Harris Poll of about 2,000 people in the United States found that about three out of 10 survey respondents said they have at least one tattoo.

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But the FDA has not approved any inks for injection into the skin for cosmetic purposes. Research has shown that tattoo ink sometimes contains pigments used in printer toner or car paint and can be contaminated with bacteria or mold, according to the FDA. The agency states there’s “no surefire way to tell if the ink is safe.”

The Alliance of Professional Tattooists, a nonprofit organization that advocates for safe tattooing, states on its website that before getting a tattoo, people should observe the artists at work. If an artist does not wash his or her hands before and after each tattoo, wear clean gloves or use high-level disinfectants, “you should walk away,” according to the organization.

The doctors in Australia knew something had triggered the woman's immune system to respond — but they did not know what, or why the reaction had taken 15 years since she got her first tattoo, said Bryant, a hematologist at the Royal Prince Alfred Hospital in Sydney.

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“I think there's absolutely no way to know how common it is,” he told CNN, adding: “Most people who have tattoos have absolutely no problems.”

The woman had noticed the lumps under her arms during a self-examination, about two weeks before she went to the clinic for evaluation.

The case report, published Monday, said she did not have a fever, night sweats, trouble breathing or unexplained weight loss — all of which are symptoms of lymphoma.

But she did have one of the most telling signs of the disease: swollen lymph nodes.

Lymphoma starts when white blood cells that fight disease mutate and multiply, “causing many diseased lymphocytes that continue multiplying,” according to the Mayo Clinic. That allows the cells to continue living, according to the Mayo Clinic, causing “too many diseased and ineffective lymphocytes in your lymph nodes and [causing] the lymph nodes to swell.”

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In this case, however, it was simply thought to be tattoo ink: For 15 years, the woman had a black-ink tattoo covering her back, and she later added one on her shoulder.

She told doctors that her tattoos would sometimes become itchy and swollen, but that her skin would then return to normal.

“We believe that this case highlights the importance of a careful tattoo history and physical examination,” the authors wrote in the report.