[185] Is the CD44+/CD24-Phenotype a Biologically Significant Subgroup among Triple Negative Breast Cancers?

Rachel Kaplan, Lucy Lee, Jiong Yan, Yi-Fang Liu, Paul Chadwick, Stefano Monni, Sandra J Shin. Weill Cornell Medical College, New York

Background: Recent studies have reported that CD44+/CD24- epithelial tumor cells are most common in basal-like carcinomas and that patients with tumors of this phenotype experience an unfavorable prognosis. The question of whether this phenotype within the basal-like molecular subtype has common biologic behavior or significance remains unanswered. Triple negative breast cancers (TNBC) which lack protein overexpression for ER, PR and HER-2/neu are almost entirely of the basal-like molecular subtype. The goal of this study was to identify TNBC exhibiting the CD44+/CD241 phenotype and identify any common clinicopathoogic variables which may further define this subgroup.
Design: After confirmation of negative ER (<1%), PR (<1%) and HER-2/neu (0 or 1+) status by immunohistochemistry (IHC), TNBC specimens of 162 patients were studied. Using a tissue microarray platform, IHC staining for CD44, CD24, EGFR, CK5 and CK14 were performed. For CD44, CD24 and EGFR, staining in >10% of tumor cells of any intensity was considered a positive result. For CK5 and CK24, staining in >5% of tumor cells of any intensity was considered a positive result. Results were recorded and data were statistically analyzed.
Results: 146 TNBC cases were interpretable for all immunostains studied. 132 of 146 (90%) were positive for at least one basal marker (EGFR, CK5, CK14). TNBC subclassified into the following CD44/CD24 subgroups: 42 were CD44+/CD24+; 76 were CD44+/CD24-, 12 were CD44-/CD24+; 16 were CD44-/CD24-. No significant association at the 0.05 level was identified when comparing subgroups to clinicopathologic variables of age, tumor size, nodal status, histologic type (ductal, lobular, other), histologic grade, presence of in-situ carcinoma or lymphovascular invasion.
Conclusions: CD44+/CD24- phenotype was the most common subgroup in our cohort of TNBC. However, patients in this subgroup did not share common clinicopathologic factors at any statistically significant level. Our findings suggest that although the CD44+/CD24- phenotype is prevalent in TNBC, it does not convey particular biologic significance of such tumors in this basal-iike molecular subgroup.
Category: Breast

Monday, February 28, 2011 1:00 PM

Poster Session II # 71, Monday Afternoon


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