An 83-year-old female has a biopsy

[Asclepius1]

An 83-year-old female has a biopsy of an ulcerated nipple lesion
that is interpreted as Paget's disease. A biopsy of the underlying
breast tissue will most likely show which of the following?
A. Acute mastitis
B. Ductal carcinoma in situ
C. Intraductal papilloma
D. Invasive lobular carcinoma
E. Normal breast tissue

[usmle2005]

My guess is Paget involves the duct system to cause ductal carcinoma.

[Asclepius1]

Yes, thats correct, the answer is B. Ductal carcinoma in situ. Very good!

[FreeSpirit]

DCIS - Ductal Carcinoma In Situ

Ductal carcinoma in situ, or DCIS, is the most common kind of non-invasive breast cancer. It is ductal because the cancer is confined to the milk ducts—which are the "pipes" that bring milk from the lobules to the nipple. Carcinoma refers to any cancer that begins in the skin or other tissues that cover internal organs—such as breast tissue. In situ or "in its original place" means that the cancer has not spread to any surrounding tissues.

DCIS is generally detected by a mammogram. Cancer cells inside the ducts appear on the mammogram, and may appear along with tiny specks or calcifications—the buildup of material left from dead cancer cells.