MKI67 and neoplasm: Even in its less advanced stages, breast cancer is more aggressive and associates with an increased rate of sentinel lymph node metastases in patients below 50 years old, the tumour size exceeds 20 mm, with the presence of peritumoral lymphocytic infiltrate, positive Ki-67 and bcl-2, an alteration of T helper (Th) lymphocytes function, increased immune suppression through IL-2 decrease, signalled by blastic transformation indexes modifications and a drop in IL-2 production (p<0.01).