CA9 and invasive ductal breast carcinoma: Her pathological examination revealed two heterogeneous tumor components in the kidney: typical CCRCC [CD10+, Vimentin+, carbonic anhydrase IX (CAIX)+, paired box gene 8 (PAX-8)+, 3% Ki-67 proliferation index) as well as multifocal metastatic invasive ductal carcinoma of the breast (estrogen receptor (ER) 50%+++, GATA binding protein 3 (GATA3) +, Human epidermal growth factor receptor-2 (HER-2) 1+, and 20% Ki-67 proliferation index).