An adenoma is a benign tumor and I think that you will not be able to "culture" these cells. At best you will be able to maintain more or less surviving these cells for one week. If you want to culture them, you should immortilized them, but you will therefore consequently modify their biological behavior.
I think you have to add growth supplement with medium. I never use adenoma cells but I used to culture cells from ameloblasoma which is also a kind of benign tumor. And for those cells I need to use keratinocyte cerum free medium with growth factor supplement. may be it can help you.