Usefulness and limitations of E-cadherin and β-catenin in the classification of breast carcinomas in situ with mixed pattern

BACKGROUND: The distinction between lobular neoplasia of the breast and ductal carcinoma in situ has important therapeutic implications. In some cases, it is very difficult to determine whether the morphology of the lesion is ductal or lobular. The aim of this study was to evaluate the value of E-cadherin and β-catenin expression through the immunophenotypical characterization of carcinoma in situ with mixed pattern (CISM). METHODS: A total of 25 cases of CISM were analyzed considering cytology/mixed architecture (ductal and lobular), nuclear pleomorphism, loss of cell cohesion, and presence of comedonecrosis. The immunophenotype pattern was considered E-cadherin positive and β-catenin positive, or negative. RESULTS: Nineteen (76%) cases presented a mixed cytology and / or architectural pattern, two (8%) presented nuclear pleomorphism, two (8%) presented mixed cytology and nuclear pleomorphism, and two (8%) presented comedonecrosis and nuclear pleomorphism. A complete positivity for E-cadherin and β-catenin was observed in 11 cases (44%). In one case, the lesion was negative for both markers and showed nuclear pleomorphis. Thirteen lesions showed negative staining in areas of lobular cytology and positive staining in cells presenting the ductal pattern. CONCLUSIONS: The expression of E-cadherin and β-catenin, combined with cytological and architectural analysis, may highlight different immunophenotypes and improve classification of CISM. VIRTUAL SLIDES: The virtual slide(s) for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/1693384202970681