The histologic type of breast cancer may not always be immediately obvious. Immunstaining a tumor for E-cadherin and high molecular weight (HMW) cytokeratins can aid in classifying the tumor.
Parameters:
(1) immunostaining results for E-cadherin
(2) quality of the E-cadherin control (as well as staining in adjacent normal ducts)
(3) immunostaining results for HMW cytokeratin
(4) quality of the HMW cytokeratin control
If an control is inadequate then the immunostain should be repeated.
E-Cadherin
HMW Cytokeratin
Interpretation
negative
positive
lobular carcinoma
positive
negative
ductal carcinoma
negative
negative
mammary carcinoma
positive
positive
mammary or ductal carcinoma
where:
• HMW cytokeratin staining in a lobular carcinoma will show cytoplasmic staining, often darker in the perinuclear region.
• Lobular carcinoma in situ can show comedonecrosis.
• Ductal carcinoma in situ can extend into lobules ("cancerization of lobules").
• The histologic pattern may affect the decision whether to call a tumor infiltrating mammary, lobular or ductal. The presence of a linear, Indian file growth patterns should at least prompt consideration of a lobular component. Many pathologists will call a cancer ductal if in doubt.
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