Keratoacanthoma Centrifugum Marginatum: Response to Acitretin.

: A previously healthy 70-year-old woman presented with a 5-month history of an asymptomatic keratotic, papulonodular plaque on her right forearm. The lesion started as a follicular papule followed by progressive peripheral proliferation. No record of trauma, contact with any chemicals, use of immunosuppressive drugs, or history of neoplasm was noted. Clinical examination showed an arciform plaque of 10×5 cm, with infiltrated raised borders and central atrophy (Figure 1). Drops of yellowish material exuded from the coalescent nodules constituting an elevated and indurate border. Results from physical and laboratory examinations revealed no internal organ malignancy. The remainder of the physical examination (x-ray of the forearm and serologies for HIV, hepatitis, and syphilis) was normal.