In March, 2001, a 38-year-old man presented with painful, sometimes tender, lumps in his armpits. The size of the lumps fl uctuated—sometimes, their diameter reached 20–25 mm, so it was painful for the patient to have his arms by his sides. The lumps had been present since the beginning of the year. The patient had no history of fever, weight loss, or night sweats. He had smoked cigarettes for 10 years, but otherwise had no notable medical history—except for hepatitis B, from which he had fully recovered. Examination revealed tender, enlarged (diameter 10–25 mm) lymph nodes in both armpits, especially the left armpit. The only other fi nding of note was that the patient had many tattoos, dating back 20 years, on his arms, chest, abdomen, and back. Blood tests, including serological tests for hepatitis B virus, HIV, Epstein-Barr virus, cytomegalovirus, and toxoplasmosis, showed nothing of note. CT of the chest showed large lymph nodes in the axillae, and sporadic bullous dystrophy. We excised three lymph nodes, for analysis. They were dark grey, indicating the possibility of melanoma. However, histopathological analysis showed reactive follicular hyperplasia and sinus histiocytosis, implying reactive lymphadenopathy rather than cancer. Many histiocytes contained black pigment. We diagnosed reactive lymphadenopathy caused by tattoo pigment. The lymph nodes regressed spontaneously. When last contacted, in January, 2008, the patient was well, and said that he had had only one further episode of lymph-node swelling in the intervening 7 years. Tattoo pigments are taken up by macrophages, that migrate through lymph vessels to lymph nodes—which can be distant from the tattoo. The resulting reactive lymphadenopathy is like that found in skin diseases. Lymph nodes can reach a diameter of 3 cm, which might ordinarily be held to indicate cancer; macrophages in lymph nodes can take up 18-fl uorodeoxyglucose, causing cancer to be suspected (wrongly) on PET scanning. Since tattooing is becoming more common in Europe and North America, we expect the incidence of tattoo-induced lymphadenopathy to increase. The onset of lymph adenopathy can be delayed, so doctors should not forget to ask, if appropriate, whether the patient has had a tattoo removed. However, lymphadenopathy caused by tattoos remains a diagnosis of exclusion.