If cells are preserved in DCIS than why these markers would be positive?

If cells are preserved in DCIS than why these markers would be positive?

The myoepithelial cells are the outermost lining of the ducts and lobules of the breast which produce a basement membrane layer( outer to the myoepithelial layer) have a contractile function.

The breaching and disintegration of this layer by carcinomatous cells marks the evidence of invasive carcinoma.

But in DCIS, the cells don’t breach the basement membrane, which means the myoepithelial layer is preserved. Hence, the p63 marker for myoepithelial cells is positive