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Difficulty: HardPathology and Biopsy Interpretation

A 55-year-old woman is evaluated in the breast clinic after a routine screening mammogram demonstrated a new cluster of fine, linear, and branching microcalcifications in the upper outer quadrant of her right breast. She has no palpable breast masses, skin dimpling, or nipple discharge. A stereotactic core needle biopsy of the calcifications is performed.

Histopathologic examination of the biopsy specimens reveals enlarged terminal duct lobular units completely expanded by a monomorphic population of atypical epithelial cells forming rigid, punched-out secondary lumens. The central portions of these involved spaces contain abundant eosinophilic amorphous debris with karyorrhectic nuclei. Associated microcalcifications are present within this central debris.

Immunohistochemical staining is performed and demonstrates a continuous, intact rim of p63 and smooth muscle myosin heavy chain (SMMHC) positive cells surrounding the involved spaces. The neoplastic cells exhibit strong, diffuse membranous staining for E-cadherin.

Based on the biopsy findings, which of the following is the most accurate diagnostic interpretation?

  1. A
    Atypical ductal hyperplasia
  2. Ductal carcinoma in situAnswer
  3. C
    Invasive ductal carcinoma
  4. D
    Lobular carcinoma in situ
  5. E
    Usual ductal hyperplasia

Answer

Ductal carcinoma in situ
The biopsy reveals expanded ducts filled with monomorphic atypical cells and central necrotic debris with microcalcifications. These architectural and cytologic features are classic for high-grade ductal carcinoma in situ (DCIS). Furthermore, the continuous rim of p63 and SMMHC positive cells confirms an intact myoepithelial layer, definitively ruling out invasive disease. Finally, the positive E-cadherin staining confirms a ductal rather than lobular origin.

Step-by-Step Solution

1
Analyze the clinical and architectural presentation
A subclinical breast lesion identified by microcalcifications on screening mammography, showing expanded ducts with monomorphic atypical cells and central necrosis (comedonecrosis).
This establishes a high-grade, neoplastic process within the breast ducts.
2
Interpret the myoepithelial immunohistochemical markers (p63, SMMHC)
The continuous, intact rim of p63 and SMMHC positive cells confirms the presence of an intact myoepithelial cell layer.
An intact myoepithelial layer proves that the atypical cells have not breached the basement membrane, confirming the lesion is in situ and ruling out invasive carcinoma.
3
Interpret the epithelial immunohistochemical marker (E-cadherin)
Strong, diffuse membranous staining for E-cadherin is observed.
E-cadherin is a cell adhesion molecule retained in ductal carcinomas but classically lost in lobular carcinomas (due to CDH1 mutations), distinguishing this as a ductal proliferation.
4
Synthesize the diagnostic features
An E-cadherin-positive, in situ ductal proliferation with prominent comedonecrosis is established.
These combined findings are definitively diagnostic of high-grade ductal carcinoma in situ (DCIS).

Key Concept

The diagnosis of ductal carcinoma in situ (DCIS) relies on identifying malignant ductal cells (E-cadherin positive) confined within the ductal basement membrane (intact myoepithelial layer confirmed by p63/SMMHC) accompanied by classic architectural features such as comedonecrosis.
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Topics

Pathology and Biopsy Interpretation

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