FICTION Technique-A Candidate for the Assessment of HER2 Status in Breast Invasive Carcinomas.

Background and Objectives: The assessment of HER2 status in invasive breast carcinomas (IBCs) is critical for determining treatment strategies. The aim of this study was to evaluate the FICTION technique as a potential method for assessing HER2 status and to compare it with the standard sequential immunohistochemistry (IHC)-in situ hybridization (ISH) assays. Materials and Methods: This study included 49 patients diagnosed with invasive breast carcinomas. HER2 status was assessed using both IHC+FISH and FICTION techniques, and the results were compared. Results: Comparative analysis demonstrated an 83.67% categorical agreement between IHC and IF using the ASCO/CAP system. The percentage of cells showing any degree of HER2 protein expression was higher with IF (73.77%) than with IHC (60.71%) (p = 0.00026). The in situ hybridization assays showed an excellent agreement, with a 90% or higher concordance. The concordance of the ASCO/CAP group classification of cases using both ISH assays (FICTION and standard FISH) was high (85, 7%). Agreement was 100% for the final classification of cases (Her2 positive/negative). Conclusions: We compared standard tests for Her2 protein expression and the gene copy number with a modified FICTION protocol. The study showed moderate agreement between IHC and IF for Her2 protein and excellent agreement between FISH and FICTION ISH for the gene copy number. Final Her2 status was unaffected by low IF IHC concordance. Optimizing the FICTION protocol could improve results. Combining protein and gene assays may enhance IBC patient stratification.