Acridine orange-DNA complex in actinic keratosis

Electron microscopy processing and staining of nuclei were used to localize reaction products of acridine orange staining in actinic keratosis of human skin. Electron-dense granules about 10-100 nm in diameter were seen exclusively in the euchromatin portion of the nucleus. Almost all tumor cells had granules (mean = 65; SD = 26). These granules were also occasionally observed in the dermal connective tissue cells in the lesion. However, the mean number of 10 granules seen in these cells was definitely less than that of tumor cells. Normal skin controls did not have granules except occasionally in the basal cells of the epidermis.