Cherry tree disease--woodturners, please look?

Recently my neighbor cut down three wild cherry trees (very small fruit, large stone). On two of the trees were large round "infections" which I presume to be cankers. Someone told me these are valuable to bowl turners, and I'd like to donate them if they're of any value. I am a furniture woodworker by trade, but I rarely turn, so I'm not certain of the significance of these cankers, nor what they look like inside. Can anyone enlighten me with regard to these growths?