First, it needs to be examined thoroughly for possible cancer risks. If there is any likelihood of cancer it will have to be biopsied and taken care of.
If it is not malignant then it can be cosmetically taken care of with laser. Most commonly these pigmented brown spots tend to be in the top layer of the skin and are called Solar Lentigos. They can be easily removed with a pigment laser. Usually couple of treatments are required at the most.