Growing plaque on foot.

An 82-year-old African American woman with a history of pancreatic cancer came into the clinic for evaluation of a growing, asymptomatic lesion on her right dorsal foot. She first noticed the lesion a year ago, when it was pinpoint size. It was now a 2.5 cm-by-1 cm hyperpigmented plaque. The lesion was dark brown and black and had irregular borders. It also had a central hyperkeratotic area. There was no inguinal lymphadenopathy. What is your diagnosis? How would you manage this condition?