Hi Brenda,
We use Xian Fang Huo Ming Yin to treat both breast cancer as well as prevent lymphedema post-mastectomy. It has an affinity for the ST channel, so if that's where the MCT is, then it may help.
If the MCT is not Damp Heat in origin, but occurring in a Blood deficiency and Blood stasis case, then Xue Fu Zhu Yu Tang is my first pick. XFHMY does work well in general, though, for tumors that show up in Damp Heat types of pictures, and where there is difficult wound healing post-op. It's also especially helpful for tumors of the appendages. In addition, it's a safe formula to try if you're in doubt. I've even used it post-operatively in overtly Qi deficient patients without any adverse effects.
Hope that helps you out!
Steve