Pathological homogeneity and utility in the genetic diagnosis of paired mirror samples from breast cancer 10G-vacuum-assisted biopsies using a novel longitudinal dividing device.

Background: The growing need for immunohistochemical and genetic testing often results in shortage of breast cancer vacuum-assisted biopsy (VAB) samples. Their value has become increasingly important with improvements in neoadjuvant chemotherapy outcomes. To enhance diagnostic utility, the longitudinal division of a single VAB sample can provide matched "mirror samples." We adapted a prostate biopsy tissue divider for use with 10G-VAB breast cancer specimens and evaluated its feasibility for pathological and molecular analyses.

Methods: A total of 100 10G-VAB specimens from 32 patients were longitudinally bisected using the dividing tool. The pathological concordance between the paired mirror samples was assessed by histological examination. Their suitability for DNA and mRNA analyses was also evaluated by next-generation gene panel sequencing and microarray-based gene expression profiling.

Results: Of the 72 samples confirmed to contain malignant tissue, 70 (97.2%) exhibited high pathological concordance between the mirror pairs. The remaining two samples (2.8%), derived from the tumor margins, exhibited discordant histological findings. Moreover, gene panel testing (n = 8) and comprehensive gene expression profiling using microarray (n = 8) were successfully performed on all of the mirror samples (n = 16).

Conclusion: The longitudinal division of breast cancer VAB tissue using a specialized dividing device results in anatomically matched mirror samples with high pathological fidelity. These specimens are suitable for advanced molecular diagnostics, thus providing a valuable tool for clinical practice and translational studies.