CA9 and neoplasm: Immunohistochemistry results deemed the tumor cells positive for expression of Ki-67 (+, about 15%), PAX-8 (+), carbonic anhydrase 9 (CA9) (+), vimentin (foci +), CD10 (+) and negative for expression of markers such as chromogranin A (CgA) (-), melan-A (-), a-inhibin (-), calretinin (-), cytokeratin 7 (CK7) (-), RCC (-), and CD117 (-) (Figures 2c,d).