Not clear on what you said - 20/28 in. lump? I would think if you had a lump this size you'd look pregnant. Your pancreas isn't big enough to support a growth that large.
Cyst? what other symptoms have you?
I had an ultra sound which showed a huge cyst. The ultra sound was followed with a CT scan. I had a very rare type of cyst which was removed. It wasn't cancer and I'm doing great.