A woman in Australia may have contracted a condition resembling cancer due to tattoos in her skin that doctors originally thought was lymphoma. Doctors put her enlarged lymph node under a microscope and found that black tattoo pigment from a 15-year-old tattoo caused her immune system to start reacting, according to a study published in the journal Annals of Internal Medicine.

The woman, who is now 30, came in to the doctor with lumps under her arms that had popped up two weeks before. After conducting a body scan, they found more enlarged lymph nodes in her chest. Almost always, it turns out to be lymphoma, but scientists were surprised what they found when they looked at it further.

Doctors removed a lymph node that was located in her armpit, and they were able to find a cluster of immune cells packed with black pigment. They think it came either from a large tattoo on her back or a smaller one on her shoulder.

“Decorative tattooing is associated with acute complications, such as pain, infection, and hypersensitivity. Delayed reactions also occur, including regional lymphadenopathy that may masquerade as malignant disease (1–3),” reads the intro to the paper.  “A 30-year-old woman presented to our clinic reporting a 2-week history of bilateral axillary lumps noted on self-examination. She had no fever, night sweats, weight loss, or pulmonary symptoms. She had a history of cluster headaches and had previously had breast augmentation surgery at age 19 years. Her only medication was an oral contraceptive pill. She was a nonsmoker with no relevant family history. On examination, numerous rubbery nontethered nodes up to 1.5 cm in diameter were felt in both axillae, with no other palpable lymphadenopathy. Her chest was clear to auscultation, and no hepatosplenomegaly was present. A large black-ink tattoo that had been present for 15 years covered her back. Another black-ink tattoo on her left shoulder was 2.5 years old.”