[263] Analysis of CD34, CD117, and Ki-67 Expression in 33 Cases of Phyllodes Tumor of the Breast

YS Noronha, AS Raza, DR Chase, CA Garberoglio, P Chu, LM Weiss, J Wang. Loma Linda University Medical Center, Loma Linda, CA; City of Hope National Medical Center, Duarte, CA

Background: Phyllodes tumor of the breast is an uncommon stromal neoplasm which can behave in a benign or malignant manner. The aim of this study was to evaluate the expression of CD34, CD117 and Ki-67 in phyllodes tumor (PT) of the breast, and attempt to correlate the staining pattern with tumor grade by morphology.
Design: Immunohistochemical expression of CD117, CD34 and Ki-67 was studied on formalin-fixed, paraffin-embedded archival tissue material from 33 cases of phyllodes tumor of the breast retrieved from the California Tumor Tissue Registry (CTTR). All 33 cases were reviewed by the authors and classified into three categories based on the current WHO criteria. Histologically, there were 21 low grade, 6 borderline, and 6 malignant (high grade) tumors. All patients were female and ranged from 13 to 86 years of age.
Results: All six histologically malignant PTs were positive for CD117 (100%), but only one marked with CD34 (16.67%). The majority of histologically low grade PTs were positive for CD34 (18/21, 85.7%) while CD117 was positive in fewer cases (7/21, 33.3%). The histologically borderline tumors were positive for CD34 in all cases (6/6, 100%) while CD117 was positive in most cases (5/6, 83.3%). Ki-67 staining ranged from 4%-20% in malignant lesions, <1%-10% in benign PTs and 2%-15% in borderline PTs.
Conclusions: Histologically benign or low-grade PT showed frequent expression of CD34 while CD117 was expressed less often. The morphologically malignant PTs, however, showed a relatively low CD34 expression but all expressed CD117. These findings are in agreement with previous reports of CD34 as a useful marker for histologically benign but not malignant PT. Additionally, there appears to be increasing CD117 expression with increasing degree of malignancy. In our study, the Ki-67 proliferative index did not distinguish morphologically benign from malignant PT. However, additional study with more complete follow-up information is necessary to determine if there is a correlation between proliferative index and biologic behavior.
Category: Breast

Tuesday, March 10, 2009 1:00 PM

Poster Session IV # 15, Tuesday Afternoon