Individual cells have low grade nuclear atypia. Some cells have signet ring appearance. It typically occurs in the central portion of the breast as a round, 2-3 cm nodule with cystic change and hemorrhage. Complex papillary projections and cribriform glands consist almost entirely of epithelial cells without myoepithelial cells. Fibrovascular stalks are less prominent than benign intraductal papilloma.
Tumor cells have low nuclear grade, inconspicuous nucleoli, and low mitotic activity.
Prognosis is excellent with low frequency of lymph node metastasis and tumor recurrence, if completely excised D. Medullary Carcinoma Medullary carcinoma can be quite large, soft on palpation, hemorrhagic and necrotic. Fibrous stroma should be limited in amount. A small portion of the tumor may undergo squamous metaplasia or contains papillary, glandular elements. In the latter, cartilaginous, osteoblastic and rhabdomyoblastic elements occur. The areas of poorly differentiated ductal carcinoma may be limited.