Immunohistochemical (IHC) staining of the first cluster (Figure 1) demonstrated retention of myoepithelial markers—smooth muscle myosin heavy chain (SMMHC; Figure 1E), p63 (Figure 1F), CK5/6 (Figure 1G), and S100 (Figure 1H)—at the periphery of all expanded acini, supporting a diagnosis of DCIS. Here, KRT5 is linked to ductal breast carcinoma in situ.