A 6-month-old boy is brought to the clinic because of a raised red lesion on his scalp (Figure A). His mother first noticed the lesion at birth and reports that it has increased in size over the past 2 months. The patient was born at term via uncomplicated vaginal delivery and has no known medical problems. He is breastfed with formula supplementation and takes only vitamin D. Vital signs are within normal limits. Physical examination is unremarkable except for the scalp lesion. What is the most appropriate next step in management?