Study of Tattoo Colorants in Skin by Conventional and Polarized Light Microscopy

Tattoos are a common practice in the 21st century. Although most modern pigments are organic and made of vegetable or plastic compounds, they still sometimes elicit an adverse reaction in the skin. Identifying the tattoo pigment in such biopsies is not always an easy task. To study how tattoo inks appear in the skin, we injected 14 different colors of commercial tattoo ink into normal skin obtained from a mastectomy specimen. One unstained section was obtained from each case, as well as one section stained with hematoxylin-eosin from each case. All sections were observed under the microscope. Stained and unstained sections were also examined under polarized light. We did not observe any modification of the ink color with the staining process with hematoxylin-eosin. However, some pigments appeared differently in stained and unstained sections than in the vial. Pink was the most difficult color to identify from the eosinophilic tissue. None of the colors showed any birefringent particles. However, in some unstained slides under polarized light, the color of the pigment appeared more similar to the one in the vial than in the stained slide.