Histopathology and X-ray microanalysis of foreign material on facial keratoses

Opaque exogenous material was frequently observed on the surface of keratoses during routine sign out by one of us (H.K.). To investigate this material further, 300 consecutive seborrheic keratoses were reviewed: 100 cases from the face of women, 100 cases from the face of men, and 100 cases from the trunk of men and women. All cases were evaluated by light microscopy for the presence and quantity of exogenous material, and 14 cases were studied by x-ray microanalysis to assess its composition. The material was present on 54% of facial keratoses from predominantly older women (mean age 67 years), 5% of facial keratoses from men, and 9% of truncal keratoses from men and women. The x-ray microanalysis showed the presence of a variety of elements, including titanium (13 cases), silicon (12 cases), iron (9 cases), aluminum (8 cases), magnesium (8 cases), zinc (4 cases), barium (2 cases), and bismuth (2 cases). We believe that the exogenous material represents cosmetic products such as colored facial cosmetics, sunscreens, and moisturizers. Further, because the exogenous material was found predominantly on facial keratoses of older women, the presence of this material in a specimen may serve as a clue to the patient's gender, age, and biopsy site.