ERBB2 and breast carcinoma: In breast cancer, for example, use of cytologic specimens for fluorescence ISH (FISH) to evaluate HER2 status revealed that FISH analysis of cytologic specimens produced more accurate HER2/chromosome enumeration probe (CEP) 17 signal ratios and HER2 copy numbers than histological specimens, as CEP17 is easily lost during histological sectioning.9, 10, 11, 12, 13, 14, 15