Pre-cancerous mole?

Just had complete excision of large mole. Doctor said results came back very abnormal cells but not malignant yet. Now I must go back for further incision. Not sure why as entire lesion was removed. It is already a large incision and still healing. On top of shoulder so could not lift or carry things as it would strain against the stitches. Is this bigger incision really necessary? Can the result come back differently after second cut?

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