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Topical EMLA Anesthetic May Poke Holes in Your Biopsy

Dermatopathologists saw EMLA-related changes that obscured the histologic features of cutaneous biopsies.

The topical anesthetic EMLA cream (2.5% lidocaine and 2.5% prilocaine in an oil-and-water emulsion) is widely used for curettage, venipuncture, or lumbar puncture and before injecting local anesthesia for minor surgical procedures, such as skin biopsy. EMLA is frequently used in the pediatric population, with cutaneous adverse reactions rarely reported. This small study alerts us to changes in histology related to this local treatment.

The authors reviewed 13 skin biopsy specimens taken from children (mean age, 3.6 years) after application of EMLA for anesthesia. Four patients were found to have erythematous and squamous diseases; four, keratinization disorders; three, bullous disease; one, suspected storage disease; and one, suspected connective tissue disease. In addition to evidence of the disease, H & E staining and electromicroscopic examinations showed histologic changes in 70% of the biopsies, including diffuse pallor with swollen upper keratinocytes (in 54%), sharp vacuolization of the basal keratinocytes (61%), destruction of the basal layer (61%), and local or large subepidermal cleavages (69%). The ultrastructural features included vacuolization of basal, spinous, and granular keratinocytes; marked enlargement of intercellular spaces without desmosomal alteration; and vacuoles in dermal fibroblasts, sweat glands, and hair follicles. Electromicroscopic examination revealed cell vacuoles in the epidermis, dermis, or both in three biopsy samples that appeared normal in H & E–stained sections. Additional skin biopsies taken from skin not exposed to EMLA in six patients showed none of these changes.

Comment: EMLA is one of the topical anesthetics preferred by practicing dermatologists. These histologic and electron microscopic findings associated with its use resemble results associated with interface dermatitis and mechanobullous and storage diseases. Therefore, when such disorders arise in the differential diagnosis of your patient, EMLA should be used cautiously or avoided. As the authors note, if you still prefer this anesthetic method, a note in the pathology requisition form is necessary to alert your dermatopathologist to avoid misdiagnosis of EMLA-related changes.

— Angelica Selim, MD

Published in Journal Watch Dermatology September 21, 2007

Citation(s):

Cazes A et al. Histologic cutaneous modifications after the use of EMLA cream, a diagnostic pitfall: Review of 13 cases. Arch Dermatol 2007 Aug; 143:1074.

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