Suggest Treatment For Brain Tumor

My mother in law recently had a MRI done. The results showed to have a hazy area of location were a tumor once was. Could this matter be serious or not? The radiologist that removed the tumor in the past is going to review the newest MRI to get a conclusion. For now the Oncologist suggested for a steroid to be taken to reduce the swelling of same area in brain until Radiologist is able to visit with my mother in law.