Epidermal vacuolation: an artifact due to injection of local anesthetics

To elucidate the mechanism of vacuolation frequently encountered in the normal epidermal cells surrounding skin tumors, 0.5 and 1.0% procaine hydrochloride, and 1.0% lidocaine hydrochloride with and without epinephrine were injected either i.d. or s.c. into mature white male rabbits, and the sites of injection were biopsied either immediately or after 15 min. the epidermis of the site of intradermal injection showed a significant increase in the number of vacuolated cells in contrast to the site of s.c. injection (p less than 0.001) irrespective of the kinds of local anesthetics and the time lapse from injection to biopsy. Electron microscopy revealed vacuole-formations without limiting membrane in the cytoplasm of the keratinocytes. It is suggested that the local edema in the upper dermis caused by injection of anesthetics gives rise to edema and vacuolation of overlying epidermal cells, and that i.d. injection of local anesthetics may be regarded as a cause of epidermal vacuolation.