CXCL13 and neoplasm: Although we could not demonstrate the correlation between HER2‐AAb and HER2 expression, we observed significant associations of tumor‐infiltrating B cells and CXCL13‐positive immune cells with HER2 expression (Figure 6), suggesting that a certain concentration of HER2 induced a humoral immune response which may have led to the production of HER2‐AAb.