During a routine skin examination in the dermatology clinic, Sarah, a seasoned nurse, encounters Mr. Rodriguez, a 55-year-old man with a history of excessive sun exposure. Mr. Rodriguez presents with a suspicious skin lesion on his back, which he noticed has changed in size and appearance over the past few months. Concerned about the possibility of skin cancer, Sarah decides to use the ABCDE rule to assess the lesion. Sarah, a gerontological nurse, is evaluating a newly identified skin lesion on Mr. Rodriguez, an 82-year-old man. Using the ABCDE rule, which finding should Sarah recognize as the strongest indicator of potential melanoma in this population?