ERBB2 and breast carcinoma: The study also demonstrated the capability of SERS nanotags in the HER2 grading of breast cancer tissue samples, differentiating between 4+/2+/1+ HER2 expression levels with Raman intensity ratios of 3.67 ± 0.51, 2.17 ± 0.2, and 1.75 ± 0.15, respectively, correlating well with fluorescent in situ hybridization (FISH) analysis.