I, too, have a birthmark. ("Too"? Remember that these posts are inspired by the Encyclopedia book. Read it if you need to understand my references.)
I've had a quarter-size birthmark on my right shoulder since I can remember. It used to be dark brown and fuzzy, like a peach. My mother dutifully had it inspected at my annual pediatric appointments.
One year, while on vacation, half of it turned an unsightly greenish color, and I think my mother may have panicked; that half was removed and biopsied almost immediately. The results were negative (in other words, positive for good health) - no cancers, no infection - nothing but a mole (or, as my mother's family called them, "Wyllers").
Back at home, we scheduled a visit with a specialist to have the entire thing removed. Careful to preserve my back-modeling career, we also met with a plastic surgeon who had a procedure for taking skin from behind the ear to graft over the surgical area. The result would be blended skin instead of an unsightly 1-inch scar.
Unfortunately, the graft never "took" and I have a puffy slightly-larger-than-a-quarter-sized red mark on my back. Yeah, way better than a linear 1-inch scar.
It's a great ice-breaker at fancy dress parties where I wear strapless dresses, or at the pool when I put on a swimsuit. It always gives a new massage therapist pause; just wait 'til they touch it!
When I was in middle school, I wrote a poem about it, entitled, "The Devil on My Back." I illustrated the work with pencil drawing of a fanciful tree burl... with satanic horns. Did I mention I was a middle schooler?
All-in-all, it doesn't bother me as an adult. I only remember it's there I attend the aforementioned parties or pool events and another guest makes a small, compassionate gasp. It's as much a part of me as my hand eczema or the way my connected nerves make my finger web and throat tickle at the same time.
I live a sexy, sexy life.