It really looks like a Cornus sp.
The leaves, buds, and bark are just like Cornus sp.

If it's not Cornus florida then it could possibly be another Cornus sp. that can be found in MA like below:

Cornus sericea
Cornus rugosa
Cornus sanguinea
Cornus racemosa
Cornus obliqua
Cornus canadensis
Cornus amomum
Cornus alternifolia

I would check to see if it's a root sprout or a seedling.

Thanks, treeguy! So my first thought was right, it was the second thought that confused me. This little one had just appeared and was growing in very good soil, while the others I was transplanting were at least a year old and growing in less optimum conditions. A couple of years ago I saw the first seedlings and had no idea they were trees. They weren't in the way then so I left them to see what they did.

I'll check out those other species. The little one was growing far away from any dogwoods so it's probably not a root sprout. I think I'll move it again and I can look at the roots, but I don't want to stress it too much.

This is an older volunteer dogwood that I've assumed is Cornus florida. Do you agree? There is a very old Cornus florida next door, so seedlings are reasonable.

{{gwi:261039}}

Claire