I did some more research and found a map of regions on mass.gov. As far as I can tell, the area in question is divided between Southeast (which includes Cape Cod and the islands) and Metro West, which is confusingly east of the central and western regions.

I guess the question is, does that area have any cohesive characteristic of its own? People talk about the Cape, and Western Mass, and greater Boston. But people don't seem to talk about that area, which I am awfully glad no one has yet called "the armpit" due to its position on the map.

Mass HHS Regions Map