Immunohistochemical and molecular analyses of HER2 status in breast cancers are highly concordant and complementary approaches.

BACKGROUND: Immunohistochemistry (IHC) and fluorescent in situ hybridisation (FISH) are currently the most commonly used methods to assess HER2 status. PCR-based assays allow quantitative determination of HER2 amplification (Q-PCR) or overexpression (Q-RT-PCR), but are not routinely used. We evaluated the relevance of Q-RT-PCR for HER2 status determination. METHODS: We compared IHC and Q-RT-PCR in 466 breast tumours. In discordant or equivocal cases, five additional methods (IHC with two other antibodies, FISH, silver in situ hybridisation (SISH) and Q-PCR) were combined to determine HER2 status. Two cases with HER2 intra-tumour heterogeneity were further explored by allelic profiles analysis and HUMARA clonality determination after microdissection. RESULTS: We observed 97.3% concordance between Q-RT-PCR and non-equivocal IHC. Twelve out of 466 cases (3%) revealed discordances between the two methods. The power of Q-RT-PCR to predict HER2 status (defined by seven methods) was similar to that of IHC. Although rare, some discordances between techniques might be due to HER2 intra-tumour heterogeneity and we report two examples, one tumour containing two distinct clones, another tumour consisting of HER2 amplified and non-amplified subclones. CONCLUSION: Q-RT-PCR and IHC are highly concordant methods for HER2 status assessment, and Q-RT-PCR allows a highly reliable quantitative assessment and could be a useful adjunct to IHC.

[Sentinel node biopsy in breast cancer]. / La technique du ganglion sentinelle dans le cancer du sein: quelques considérations récentes.

As compared to conventional axillary dissection, the sentinel node technique is accompanied by reduced morbidity and shorter hospital stay. Based on available data, the use of this technique does not seem to yield higher rates of axillary recurrence. A combination of both radioisotope detection and blue dye increases the identification rate, while also reducing false-negative rate. Surgical results are optimized when preoperative lymphoscintigraphy mapping is obtained in addition to peroperative probe detection. Considering the site of injection, the subareolar injection can be easy to apply even in case of non-palpable tumours, and gives higher count rates. However, the intraparenchymal, peritumoral, injection is necessary to evidence cases of extra-axillary drainage (internal mammary, infra- or supraclavicular) that is present in about 20% of patients. With the advent of hybrid cameras (SPECT-CT), the topography of these extra-axillary nodes can be given with high precision. Use of the sentinel node technique has been accompanied by an increase in the percent of patients with node involvement, due to an increased detection of micrometastases inferior or equal to 2 mm. Following an overview of basic principles, and of the main results with the sentinel node technique we focus the discussion on several points that are still open to debate, such as: 1) which group of patients can benefit from the sentinel node technique? 2) What is the optimal methodology? 3) What is the prognostic significance of micrometastases and of isolated tumour cells? 4) What attention should be given to extra-axillary drainage?