Are there any treatments (maybe lipo?) that can reduce a fatty hump on back of neck from medical steroid use?

Thank you for your question. This fatty hump on the back of the neck can be effectively removed with liposuction. It can be done under local anesthesia with minimal oral sedation. This treatment is highly effective.
See a board certified plastic surgeon for an in person consultation/evaluation. Good luck.

"For best results in improving a buffalo hump, I recommend a hi-definition procedure like VASER Hi-Definition Liposuction. I use VASER HI-DEF with ThermiRF, Renuvion (J-Plasma), InMode BodyTite, and fat grafting to get the most fat removal, skin tightening, contour and definition. If there is any skin laxity, then it can be removed at the same time as the liposuction procedure.

I recommend getting a formal evaluation with a hi-definition physique expert. Best, Dr. Emer"

Fatty tumors of the upper back can usually be treated with liposuction. Or, it can be surgically excised with a larger incision. Some, unless quite large, can even be treated with Kybella injections. I would suggest meeting with a board certified plastic surgeon and discussing your options.