Extramammary Paget disease (EMPD) is a very rare form of skin cancer, affecting an estimated one in a million people in the U.S. It tends to grow slowly, but if left untreated, it can become invasive and spread to other parts of the body. That’s why early detection is so important.

Because it’s so rare, many doctors may never see a case in their careers. To help us understand more, we spoke with Phyu Aung, M.D., Ph.D., a dermatopathologist who specializes in rare skin cancers like EMPD.