Routine diagnostic histopathology and immunohistochemistry (IHC) of recurrent breast cancer for ER, PR, and HER2 (with fluorescence in situ hybridization [FISH] testing of HER2 where appropriate) may be a pragmatic solution to ensure that the patient actually has recurrent breast cancer [17] and to guide further patient therapies. The gene discussed is ESR1; the disease is breast carcinoma.