A 35-year-old woman has a lumpectomy for a breast mass. Histology shows malignant epithelial cells filling and expanding the ductal lumens without basement membrane invasion. There is central comedo-type necrosis with calcification. What is this lesion?

• A Invasive ductal carcinoma (IDC, NST)
• B Lobular carcinoma in situ (LCIS)
• C Phyllodes tumor (malignant)
• D Ductal carcinoma in situ (DCIS), high-grade comedo type ✓

Explanation

DCIS, high-grade comedo type, is characterized by large pleomorphic cells filling ductal lumens with central necrosis (comedo necrosis) that calcifies — forming the linear/branching calcifications seen on mammography. The basement membrane is intact (in situ). DCIS comedo type is high-grade, ER/PR negative, HER2-overexpressing, and carries a significant risk of progression to invasive carcinoma if untreated. LCIS involves lobular units with bland cells that lack E-cadherin expression and do not cause calcifications or palpable masses.

Reference: Robbins & Cotran Pathologic Basis of Disease, 10th ed.

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Written and medically reviewed by the StethoPrep medical team.