Which statement correctly describes DCIS?

• A. DCIS invades beyond basement membrane.
• B. DCIS is confined within the ducts and does not invade surrounding stroma.
• C. DCIS invades surrounding tissue.
• D. DCIS is the same as IDC.

Answer: (B)

DCIS is a non-invasive lesion where malignant cells are confined to the ducts and do not breach the basement membrane, so they do not invade the surrounding breast stroma. This confinement is what distinguishes DCIS from invasive cancers. The basement membrane serves as the barrier; when cancer cells stay inside the ducts, there is no invasion into adjacent tissue, which is why DCIS is not considered invasive cancer. The statement that it is confined within the ducts and does not invade surrounding stroma best describes its nature. In contrast, invasion beyond the basement membrane or invasion into surrounding tissue would indicate invasive carcinoma, and DCIS is not the same as invasive ductal carcinoma.