A 65-year-old man presents with a flat, irregularly shaped, dark brown lesion with varying colors and a diameter larger than 6mm on his back. What could be the potential diagnosis?
The patient's lesion, given its irregular shape, varying colors, and size larger than 6mm, has characteristics of malignant melanoma. Key features of melanoma include asymmetry, border irregularity, color variation, diameter greater than 6mm, and evolving changes. A biopsy would be necessary to confirm the diagnosis.