A pathologist reviews a resected breast mass and reports 'comedonecrosis' within dilated ducts. The duct lumens are filled with highly atypical epithelial cells with central areas of necrotic debris and calcification. The basement membrane of the ducts remains intact. What is the correct diagnosis, and what grade does this pattern signify?

• A Invasive ductal carcinoma, grade III
• B Lobular carcinoma in situ (LCIS), necrotic variant
• C Ductal carcinoma in situ (DCIS), high nuclear grade ✓
• D Sclerosing adenosis with apocrine metaplasia

Explanation

Comedonecrosis is the hallmark of high-grade DCIS (ductal carcinoma in situ), where the rapidly proliferating, high-grade malignant ductal epithelium outgrows its blood supply, producing central necrosis with dystrophic calcification visible on mammography. The intact basement membrane confirms in situ (non-invasive) disease. LCIS is characterized by small, uniform cells that do not form necrosis; invasive ductal carcinoma would breach the basement membrane.

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

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