CCL21 and ductal breast carcinoma in situ: HER2-high DCIS showed upregulation of several immune markers and chemokines, including many of those identified in the spatial transcriptomic analyses, such as CCL19, CCL21, CD19 and MSF4A1, whereas HER2-high IDC showed higher expression of several interferon-induced genes (Fig. 4b, Suppl.