My husband was sent by his GP to a dermatologist when we located a "suspect" mole. The Dermatologist took a core sample. It required 4 stitches. You can not determine the "stage" or size of the tumor by the core sample. The attempt is made to biopsy the deepest part, but the dermatologist can only do his/her best. That sample came back positive for Melanoma. The dermatologist sent us directly to MDA for surgery for the removal of the tumor and lymph nodes.
A very large part of my husbands forearm was removed to ensure they got all of the cancer. Three lymph nodes were removed. The lymph nodes came back clean. We now go every three months to MDA for full check ups - and see the dermatologist in between visits.
BTW - although a HUGE amount of tissue was removed during surgery - he only has a long scar and a slight dimple at each end. You might not even notice it until he points it out.