Hi there:
I have not heard of steroid injection.
Steroid treatment alone, has fallen out of favour. But steroid treatment along with methotrexate can help avoid recurrences.
Diet changes can help some, however not all.
IGM cases run the gamut of severity from mild and self-resolving; to continued GM activity even with double mastectomy and chest planing.
I do not say this to scare you, but to help illustrate the horrible fact that as there is no known cause, there is no known cure.
Try the least severe treatments first, then the more radical, as need be.
Be well,
jojo
First try complete diet change, eg no nightshades or high protein or inflammatory food, homeopathy from well reputed doc etc alternatives mentioned on the forum ....good luck