How important is the lymphatic massage after mastectomy?

Depends. : It really depends on if and how many lymph nodes were removed during the mastectomy. Most mastectomies are done these days with minimal or even no lymph nodes removed. These cases would not likely require any massage to be done, and would only be needed if swelling started to occur. However, if a full lymph node removal was done, then a lymphatic massage would likely be beneficial.