RÉSUMÉ
<p><b>OBJECTIVE</b>To determine how patients with infiltrating lobular carcinoma (ILC) differ from patients with the more common infiltrating ductal carcinoma (IDC), and observe the different expression patterns of E-cadherin and p120-catenin proteins in both ILCs and IDCs.</p><p><b>METHODS</b>The patients with ILC admitted to our hospital from Jan 1999 to Dec 2006 and patients with IDC from Jan 2000 to Dec 2000 were included in this study. All their pathological slides were reviewed, and their clinical data and treatment variables were analyzed retrospectively. Then the expression patterns of E-cadherin and p120-catenin proteins in both ILCs and IDCs were detected by immunohistochemistry on tissue microarray.</p><p><b>RESULTS</b>The 5-year overall survival was 81.7% for ILCs and 79.1% for IDCs (P = 0.055). The 5-year disease-free survival was 61.8% for ILCs and 83.7% for IDCs (P < 0.001). Cytoplasmic localization of p120-catenin and loss of E-cadherin expression were more common in ILCs than in IDCs. The complete losses of E-cadherin in ILCs and IDCs were 55.6% (20/36) and 20.4% (45/221, P < 0.001), respectively. The p120-catenin showed a diffuse cytoplasmic localization in 66.7% (24/36) of ILCs and 16.3% (36/221) of IDCs (P < 0.001). Interestingly, the cytoplasmic localization of p120-catenin was clearly associated with the absence of E-cadherin expression in ILCs (P = 0.002), cytoplasmic localization of p120-catenin and absence of E-cadherin expression were observed 55.6% (20/36) in ILCs compared with 4.1% (9/221) in IDCs (P < 0.001).</p><p><b>CONCLUSION</b>ILC has several specific biological and prognostic characteristics which are different in IDC. Different expression patterns of E-cadherin and p120-catenin proteins can be helpful to recognize ILC from IDC.</p>