The reliability of assessment of Ki-67 and HER-2/neu expression on breast carcinoma agarose cell blocks

Abstract

Background Assessment of multiple prognostic and/or predictive biomarkers in patients with breast cancer with good reliability and reproducibility using samples obtained by fine-needle aspiration (FNA) can be of significant clinical value. Objective The objective of this study was to determine the reliability of assessment of breast carcinoma markers, Ki-67 and HER-2/neu, on agarose cell blocks (CBs). Patients and methods FNA samples were obtained from 29 female patients presenting with primary breast carcinoma. To prepare CBs (cytoblocks), cells were fixed in 10% neutral formalin for 6–12 h, embedded in 2% agarose gel, processed using standard laboratory protocol for biopsy tissue, and paraffin-embedded. The expression of Ki-67 and HER-2/neu was evaluated by immunohistochemistry (IHC) on cytoblocks and their corresponding formalin-fixed, paraffin-embedded histological resection specimens. Results Tissue sections exhibited high Ki-67 expression in 27/29 (93.1%) invasive breast carcinoma cases, whereas 2/29 (6.9%) tumors revealed low Ki-67 immunoreactivity. MIB-1-stained CBs showed high Ki-67 expression in 24/29 (82.7%) breast carcinoma cases, whereas 5/29 (17.3%) tumors revealed low expression. MIB-1 IHC staining on agarose CBs showed 26/29 (89.6%) tumors correlation with tissue results. IHC analysis of HER-2/neu protein expression on tissue sections revealed that 23/29 (79.3%) breast carcinoma cases were negative for overexpression (score 0 or 1+) and 6/29 (20.7%) were positive for overexpression (3+). On agarose CBs, 21/29 (72.4%) invasive breast carcinoma tumors were negative (0 or 1+) for HER-2/neu overexpression, 2/29 (6.9%) showed equivocal IHC staining (2+), and 6/29 (20.7%) tumors were positive (3+). IHC staining for HER-2/neu on agarose CBs showed 93.1% correlation with tissue results. Conclusion In invasive breast carcinoma, Ki-67 and HER-2/neu (negative/positive) expression could be determined with good reliability on agar CBs prepared from FNA using standard IHC procedures.