Aims: Biotin-free polymeric visualization systems (BFPS) were compared to streptavidin-biotin systems (SABS) in the evaluation of immunoreactivity for estrogen receptor (ER) in breast carcinomas.
Methods: The anti-estrogen antibody clone SP1 was employed on a tissue microarray containing 320 breast carcinomas. Eleven different detection systems were used: six BFPS of second generation (Advance, Novolink, SuperPicTure, PicTure Max, Super Sensitive Non-Biotin HRP, and Mouse/Rabbit Polydetector HRP/DAB), one BFPS of first generation (EnVision+), and four SABS (LSAB+, EasyPath, Super Sensitive, and Mouse/Rabbit Immunodetector HRP/DAB). The slides were digitalized using the Mirax scanner and the resulting images were analyzed both by an automated method and by visual analysis using the Allred's score system considering positive nuclear staining. Cytoplasm staining was also separeted evaluated.
Results: The BFPS Advance and Novolink showed the highest scores by visual analysis, and additionally detected two positive cases which were considered negative using the other detection systems. Likewise, these systems, together with the SAB LSAB+, showed higher staining intensity by the automated method. BFPS revealed no cytoplasm staining, in opposition to the SABS.
Conclusions: The second generation BFPS, especially Advance and Novolink, provide stronger and sharper nuclear immunohistochemical signal as compared to most SABS, without nonspecific cytoplasm staining. As in few instances these detection systems show discordant results in relation to SABS, further studies correlating these findings to therapeutic response are necessary. BFPS may represent a high quality tool both for research and clinical evalutation of estrogen receptor in breast cancer.