How would you manage this lesion on the back of the arm?

In this week's case discussion, submitted by Dr Mukkamala, we look at a 70-year-old male patient who presents to his GP for renewal of his prescriptions for hypertension. 

He is offered an impromptu skin check and this lesion is found on the back of his right arm. What is your differential diagnosis here?

Update

The pathology result showed superficial spreading malignant melanoma, Breslow Thickness 0.7mm, Clark Level 3. What next?

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