Suggest Treatments For Rosai-Dorfman Disease With Eye Tumors And Lymph Nodes In An Elderly Person

Hello Doctor, My mother is around 65 years old and has been diagnosed with Rosai dorfman . She has some lymp nodes behind ears and jaw and a benign tumour behind her eye orbit and she has lost one eye vision after operating her nasal polyps. She had floaters eye for a while and now the tumour is growing behind her eyes. Apart from chemotherapy and steroid which is affecting her vision on other eye what kind of treatment is recommended and where can we find speacialised doctor for this disease as it is very rare. please help and advise...Luv and light