Immunocytochemical results for HER2 and Ki67 in breast cancer touch-smear cell specimens are reliable.

Background: Re-evaluation of the subtype of recurrent breast cancer is necessary for deciding the treatment approach, but it is often not performed due to the difficulty of obtaining tissue specimens from a recurrent lesion, etc. However, when a recurrent lesion is close to the body surface, fine-needle aspiration cells (FNA cells) can be easily obtained, and immunocytochemical (ICC) analysis of hormone receptors expression in FNA cells is said to be highly reliable. However, there is no consensus regarding ICC analysis of human epidermal growth factor receptor type 2 (HER2) expression and the Ki67 index using FNA cells.

Methods: Touch-smear cells (TSC) were prepared from resected specimens from 36 patients with primary invasive ductal carcinoma of the breast. The TSC were fixed in 95 % ethanol and subjected to ICC analysis for HER2 using HercepTest™ (Dako) and Ki67 using MIB-1™ (Dako). HER2 expression and the Ki67 index for the TSC were compared with the results of immunohistochemical analysis of histological section (HS). Statistical analyses used the kappa test and Pearson's correlation coefficients.

Results: HER2 and Ki67 were analyzed in TSC from 36 and 28 patients, respectively. The HER2 expression scores in the TSC and HS groups showed good agreement (kappa value =0.640) and significant correlation (correlation coefficient =0.860, p < 0.001). The Ki67 indexes in the TSC and HS groups also showed significant correlation (correlation coefficient =0.861, p < 0.001).

Conclusions: The reliability of ICC analysis of HER2 expression and the Ki67 index using TSC were recognized.