This is not a good sign.
Your photo shows a surprising amount of trunk decay and what looks like tiny holes from boring insects. The dark areas towards the bottom look like an opportunistic canker disease (Hypoxylon), which is secondary, only affecting trees that are already compromised.

How does the leafy canopy of the tree, particularly the part that grows from this portion of trunk look during the growing season? We'd expect it would not look well.

Unfortunately, there are no chemical controls for cankers and they cannot be stopped once they become extensive.
The only control measures available are to remove affected branches and prune back to healthy wood, which may not be possible in this case.

This page helps homeowners decide when it may be time to remove a tree: 
https://extension.umd.edu/resource/how-do-you-decide-when-remove-tree


Christine

Thanks for your quick response. The question was for my neighbor, Merry about her tree. . I have forwarded your answer to her! 
Jane