Microdermabrasion sands off about 10-15 micron depth of skin. The EPIDERMIS, the outer layer of skin is 50 - 60 microns thick. Most sun spots are thicker than 10 microns and would require a deeper peel. In this regard, Microdermabrasion is literally a feel good feel that does not last and will not erase most skin lesions.
Try a Sciton MicroLaser peel and your sunspots will be gone in the vast majority of cases.
Dr. P. Aldea