Regarding stains used by pathologists to determine types of cells...
Melanocytes in Long-standing Sun-Exposed Skin
Quantitative Analysis Using the MART-1 Immunostain
Ali Hendi, MD; David G. Brodland, MD; John A. Zitelli, MD
"PHYSICIANS WHO DIAGNOSE melanoma histologically or who evaluate the surgical margins of melanoma often face the difficulty of distinguishing nonmalignant melanocyte hyperplasia from melanoma in situ in sun-damaged skin.
...With such uncertainties, many physicians most likely err on the side of over diagnosing melanoma in sun-damaged skin to avoid the obvious medical and legal consequences of not diagnosing true melanoma.
Over diagnosis, however, leads to additional and unnecessary surgery, morbidity, and deformity."
Here is the link to the full article. Before undergoing surgeries, ask questions of your doctor and get a second opinion on the pathology if you can.