The level of IT+AS, but not total, ICCs positive for IGKC, a plasma cell marker, in the high HER2‐AAb group was also significantly greater than those in the low HER2‐AAb group (Figure 3C, D and L), suggesting that tumor‐infiltrating B cells and plasma cells were involved in the production of HER2‐AAb. Here, ERBB2 is linked to neoplasm.