Possibly ganglion cysts. I had one on the back of my hand (years before dialysis) and had it carved out by a hand surgeon.
Probably not ganglions as they tend to be on the extensor surface of the hand which is the back of the hand. More likely fibromas . These are benign soft tissue tumors made of fibrous tissue. I often see them in hands and feet on the same person. Of course I am only guessing here as I cant see them . There are other possibilities but fibromas are common.