NIS is expressed in 80% of human breast tumors in a tissue microarray with primarily intracellular localization and positive correlation with pAkt expression. (A-C) NIS immunohistochemical staining in three representative breast cancer specimens. (A) NIS-negative breast tumor. (B) Breast tumor with intracellular NIS localization. (C) Breast tumor with both intracellular and plasma membrane-localized NIS protein (arrows). (D-F) Immunohistochemical staining for pAkt in the three breast tumors shown in A-C. (G-I) H & E staining demonstrating the histopathology of the three breast tumors shown in A-C. Bar = 20 μM.