My husband has a brown area on his lips, is this normal?

Can you look at the brown area on my husbands lip. He has had it for years and his dermatologist looked at it a few months ago. He said it was fine but it still worries me. Is this normal sun damage or something more concerning? I know it has been there for at least 6 years and hasn’t changed that I can tell at all. Thanks.
Age:36
Male
Medications: sudifed,