That p63+/Her2+ cells are detected both in the myoepithelial and luminal compartments of comedo-DCIS suggests that these transitional precursors probably experience a block in differentiation into discrete p63+/Her2/neu− (basal cells of myoepithelial lineage) and Her2+/p63− (Her2-overexpressing) lineages. The gene discussed is ERBB2; the disease is ductal breast carcinoma in situ.