From what I understand, the spleen in TCM is not refering to the organ itself but to a function of the digestive system. That is, the transformation of Food into Qi and transportation of that Qi around the body. I have read that if the Stomach (yang organ) and Spleen (it's yin counterpart) are healthy then prognosis is good. Can anyone more educated than I correct (if I am wrong) and/or expand on this?

Life and Teaching of the Masters of the Far East
By Baird T. Spalding