As shown in Fig. 8, only 1.67% of breast cancer TMA cores (5/300) and 3% of cervical TMA cores (3/100) were stained by mAb Kao1 (Fig. 8E), in which Piwil2 (Kao1)-expressing cells were usually low in frequency (Fig. 8B); in contrast, all TMA cores of cervical and breast cancers were stained by mAb Kao2 (Fig. 8B). This evidence concerns the gene PIWIL2 and breast cancer.