I'm not 100%but I believe it's to do with type of melanoma. Where I live if its anything higher than our including 1b then you will be offered an slnb.
Sentinel node biopsies are used to help stage a melanoma by checking the nearby lymph nodes for cancer cells during a wide local excision. It is an optional test but is usually recommended in patients with a stage 1B or above. You can read more about this here.
Generally a sentinel node biopsy takes place at the same time as the surgery. I would discuss any concerns you have with the specialist team involved with the patients care.
