I was working on my harrow sweet pear yesterday and noticed several distinct patches in the bark of the leader where the texture was rougher, and it appeared slightly darker/sunken.

My first thought was possible fireblight canker....It is pretty rare for us, I had a few tip strikes one spring years ago (different tree) and that is the extent of my experience. I noticed no issues last year, and have several varieties that are supposed to be far more susceptible.

There were several small branches broken off by over spreading limbs in the affected region last spring

Digging my nail into one patch, the cambium was still green underneath but seemed thinner and drier than it should.

There is no weeping, or staining from previous weeping, but things are still quite dormant here.

I will try to get images later today, the weather is crap right now.

What other possible causes?