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But when the doctors sampled the lymph nodes, they were not cancerous all. However, they were black.

The ink from a back tattoo the patient received 15 years earlier had seeped into her lymph nodes, causing the discoloration. They also found that once the cells from her nodes were exposed to the ink, they became irritated, which caused the swelling and some itching.

The doctors believe she had a hypersensitivity or allergic reaction to the tattoo ink that may have occurred more than once.

In fact, after 10 months the swelling had completely subsided without any treatment or intervention.

Want to learn more about the findings? Take a look at the study here.

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