[205] HER2 Rabbit Monoclonal Antibody 4B5 and Silver SISH: High Performance in Surgical Pathology for Appropriate Patient Care

H Itoh, N Kato, A Serizawa, T Itoh, S Umemura, RY Osamura. Tokai University School of Medicine, Isehara, Japan

Background: For the daily HER2 testing, ASCO/CAP guideline requires to retest if the results of either IHC and FISH are equivocal. It has been reported that rabbit monoclonal antibody 4B5 provides excellent sensitivity, specificity, and interlaboratory reproducibility. In addition, non-fluorescent detection of HER2 gene copies, silver SISH has been recommended for routine laboratory use. This study is aimed at to elucidate whether the combination of HER2 IHC by 4B5 and HER2 SISH functions efficiently for routine HER2 testing.
Design: Tissues from 44 cases of breast cancers were subjected to the following IHC, FISH and silver SISH studies. Rabbit monoclonal antibody 4B5 was used for automated immunohistochemistry(IHC) on formalin-fixed paraffin ebedded(FFPE) sections. Interpretation was done by following ASCO/CAP guideline. Silver SISH was also performed on the consecutive sections of the same cases for HER2. Immunohistochemistry by monoclonal antibody CB11 was also done for comparison. Silver SISH resulted in countable gene copies for HER2 and CEP17. Ratio HER2/CEP17 was calculated and compared with HER2 FISH(Abbott Moleculer Inc.).4B5,CB11 & SISH were supplied from Ventana Medical Systems, Inc.
Results: For IHC and FISH, 19 cases showed 4B5+ FISH+ and 14 cases revealed 4B5- FISH-. SISH and FISH also showed excellent concordance except for one FISH+ case which was SISH-. Eight cases of 4B5 2+ were also CB11 2+, and the discordance between two antibodies were two cases, less cases of HER2 2+ by 4B5. Seven of eight 4B5 2+ case were FISH negative, one 4B5 2+ case was FISH equivocal. One 4B5 2+ cases was FISH- but SISH+.
Conclusions: Our studies suggest the combination of 4B5 and SISH could serve as the appropriate target detection system for the efficient patient care by Trastuzumab for advanced and early breast cancers.
Category: Breast

Tuesday, March 10, 2009 9:30 AM

Poster Session III # 42, Tuesday Morning