MKI67 and myoepithelial tumor: (1) Differentiation from myoepithelioma: while myoepithelioma shares cellular and IHC similarities with MECA, MECA lacks infiltrative growth, and its cellular heterogeneity is less pronounced; IHC staining with the Ki-67 antibody, characterizing cellular proliferative activity, can aid in distinguishing benign and malignant myoepithelioma, with MECA diagnosed when the Ki-67 index exceeds 10% (20).