Could A Hard Lump On The Side Of Neck Be Recurred Melanoma?

My husband was diagnosed with Stage III Melanoma in October 2013. Surgery to remove the melanoma on his left shoulder, and a lymph node showed positive. So we had the lymph nodes removed under his left arm. He has been going quarterly to Mayo about 4 hours from our home) Just got a clean bill of health (xrays and blood work) in December 2014. This week we found a hard lump on the left side of his neck...about the size of a shooter marble. We went and saw his original surgeon. He had a PET scan yesterday and is scheduled for surgery tomorrow morning to remove the lump and have it biopsied. I need to be prepared...we get the results of the PET scan tomorrow morning. What are the odds that the melanoma has spread?