How do u know when u have cancer in the belly button???

Skin biopsy: Not a common site; however,I advise a dermatolgy evaluation and skin biopsy if necessary.

Very unlikely: There are some rare instances that other cancers can spread to that area, but as a first site - it is really unlikely. If you can't shake the fear - see a doctor and ask for a CBT psychotherapy referral to learn about your medical fears and how to deal with them. A negative physical exam is a good start.