Fig. 3: Intratumoral heterogeneity of HER2 expression.

In HER2-3+ cases, it is observed that HER3+ coexists with HER-2+ and HER2-1+ staining intensities (left). Stained tumor cell proportions varied: HER2 3+ cases showed 30%–100% (median 75%) tumor area with 3+ intensity; 2+ cases covered 10%–85% (median 25%) with 2+ intensity; 1+ cases had 10%–55% (median 20%) 1+ intensity (right).