ERBB2 and breast cancer: Another study found that insulin-like growth factor 1 receptor (IGF1R) membranous and mixed (membranous and cytoplasmic) expression in BC cells was evident in HR + HER2− cases in contrast with HR−HER2+ cases, which showed cytoplasmic or diminished IGF1R expression, suggesting that luminal subtypes may benefit from targeted IGFR therapy [61].