HER2 assessment in locally advanced gastric cancer: comparing the results obtained with the use of two primary tumour blocks versus those obtained with the use of all primary tumour blocks.

Dual-block immunohistochemical assessment is an effective, practical and economic approach that is suitable for the preliminary screening of HER2. We recommend that dual-block HER2 assessment be routinely performed on resected specimens of GC. All-block assessment can be a supplement to dual-block assessment if necessary.