Estimation of hormone receptor status in fine‐needle aspirates and paraffin‐embedded sections from breast cancer using the novel rabbit monoclonal antibodies SP1 and SP2

Abstract

We describe a method of immunocytochemical assessment of estrogen receptor (ER) status on alcohol-fixed smears obtained by fine-needle aspiration (FNA) from breast cancer patients, using a commercially available rabbit monoclonal antibody anti-ER (SP1) without any antigen retrieval. A series of 40 aspirates were analyzed and the results of ER status were compared with the respective formalin-fixed tissue using the same procedure and with assessment by the classical method using the mouse monoclonal antibody 6F11 (anti-ER) with antigen retrieval on paraffin sections. Twenty-four out of the 40 cases examined were positive at least by two methods and 16 were negative for all three determinations. The results obtained in the ER immunocytochemical assay on aspirates and paraffin sections using the antibody SP1 and those obtained on paraffin sections using the antibody 6F11 were quite similar. In one case the material was insufficient to interpret the reaction in the cytological specimen and only one case, with focal positivity reaction on paraffin sections, was negative in the cytological specimen. The intensity of nuclei staining in cytological smears of breast cancer cells was stronger than that observed by traditional methods. We also assessed progesterone receptor (PR) status on 40 paraffin-sections from breast cancer patients, using a commercially available rabbit monoclonal antibody anti-PR (SP2), with the same characteristics described for anti-ER (SP1). The results were compared with assessment by the classic method with mouse monoclonal antibody 1A6 (PR) on paraffin sections and total agreement was observed. Of the 40 cases examined, 18 were positive and 22 were negative for the two determinations. We conclude that the application of the ER method on alcohol-fixed smears/paraffin sections with the rabbit monoclonal antibody SP1, and the PR method on paraffin sections with the rabbit monoclonal antibody SP2, provide several advantages, such as high sensitivity and specificity of the reaction, stronger immunostaining, shorter procedures times, and avoidance of antigenic retrieval methods.

Immunohistochemistry for estrogen and progesterone receptors in the distinction of primary and metastatic mucinous tumors in the ovary: an analysis of 124 cases

“…SP-1 and SP-2 rabbit monoclonal antibodies for ER and PR, respectively, were employed because preliminary evidence suggests that they are more sensitive than the mouse monoclonal antibodies. 53,54 Antibody localization was achieved by incubating slides for 30 min at room temperature in Envision þ -labeled polymer (DakoCytomation, Carpinteria, CA, USA) using a Dako autostainer. The slides were then incubated for 10 min at 371C in a solution containing 3% hydrogen peroxide and 3,3 0 -diaminobenzidine.…”

Predictive factors of breast cancer evaluated by immunohistochemistry

“…The results showed advantages, such as high sensitivity and specificity of the reaction, stronger immunostaining and shorter procedure times (6) . The rabbit antibodies appear to offer increased sensitivity with no apparent loss of specificity and allow a higher working dilution (24) .…”

“…For example, the rabbit monoclonal antibody SP1 can be used 10 times less concentrated than the 6F11 when using antigen retrieval (6) . However, antigen retrieval may cause false-positive stains or nonspecific background due to endogenous biotin.…”

A comparison between the novel rabbit monoclonal antibodies (SP1 and B644) and mouse antibodies for evaluating estrogen receptor in breast tumors

“…Immunostaining was evaluated considering positive those tumors in which more than 10% of the tumor cell nuclei stained. The stain intensity was also evaluated as weak (1), moderate (2), and strong (3). Results: Both rabbit antibodies against ER have similar staining pattern to each other and also to 6F11, but significantly stronger scores compared to mouse 1D5.…”

“…The technology to prepare these antibodies from a single hybridoma allows the production of antibodies with high sensitivity and specificity, high working dilutions and better cost versus benefits. According to the suppliers, the novel rabbit monoclonal antibodies could replace the mouse monoclonal antibodies because of their high specificity, lower cost, and faster technical procedure, which would not require an antigen retrieval step (3,14,24) . Several anti-ER antibodies have been used in clinical and research immunohistochemical testing, including mouse monoclonal antibodies.…”