A postmenopausal woman with a white discoloration on her breast

A 61-year-old woman presents concerned about a white discoloration on her left breast that she first noticed 6 months earlier. It itches at times, and she is worried it might be cancerous. She showed it to her gynecologist at her annual visit, and he referred her to the dermatology clinic. Physical examination of the left breast reveals a 10-cm white, ...