Methods for the diagnosis and treatment of breast cancer

1. A method for assessing the efficacy of breast cancer therapy in a non-lactating human subject who has undergone or is undergoing treatment for breast cancer, comprising determining whether or not mammary gland sodium/iodide symporter (mgNIS) is expressed in breast tissue of the subject, wherein

expression of mgNIS in the breast tissue is detected using an antibody, or a fragment thereof, specific for mgNIS, and

expression of mgNIS in the breast tissue of the is indicative of the presence of breast cancer in the subject, and an absence of mgNIS expression in the breast tissue is indicative of successful breast cancer therapy in the subject.

2. The method of claim 1 , wherein the expression of mgNIS is detected in vitro or in vivo.

3. The method of claim 1 , wherein the antibody is labeled with a detectable marker.

4. A method for assessing the efficacy of breast cancer therapy in a non-lactating human subject who has undergone or is undergoing treatment for breast cancer, comprising determining whether or not mammary gland sodium/iodide symporter (mgNIS) is expressed in breast tissue of the subject, wherein

expression of mgNIS in the breast tissue is detected in vitro using at least one nucleic acid probe that specifically hybridizes to nucleic acid encoding mgNIS, and

expression of mgNIS in the breast tissue of the subject is indicative of the presence of breast cancer in the subject, and an absence of mgNIS expression in the breast tissue is indicative of successful breast cancer therapy in the subject.

5. The method of claim 4 , wherein the nucleic acid probe is DNA.

6. The method of claim 4 , wherein the nucleic acid probe is RNA.

7. The method of claim 4 , wherein the nucleic acid probe is labeled with a detectable marker.