Are fine-needle aspiration biopsy-derived cell blocks a useful surrogate for tissue samples in breast cancer?

The diagnosis of breast cancer (BC) is based on clinical examination in combination with imaging, and confirmed by pathological assessment of core needle biopsy or fine-needle aspiration biopsy (FNAB). The biological profile of the lesion is needed to define the prognosis and establish therapy. Given the importance of an early and minimally invasive diagnosis, we aimed to verify whether the biological features detected in FNAB-derived cytological material reflect the biological characteristics of surgical samples.

We used immunohistochemistry and fluorescence in-situ hybridisation to study a panel of conventional biomarkers [oestrogen receptor (ER), progesterone receptor (PgR), Ki67, and human epidermal growth factor receptor 2 (HER2)] in FNAB-derived cytological samples included in cell blocks of 93 BC patients, and compared the results with those obtained from histological evaluation of the same parameters in surgical samples. Median immunopositive values of ER, PgR and Ki67 were similar in cell blocks and surgical samples. The concordance rates of ER and PgR between FNAB-derived cell blocks and histological samples were 98% and 84%, respectively. The concordance rates of Ki67 and HER2 between the two sample types were 90% and 96%, respectively. Tumour subtype classification for triple-negative and HER2-positive BCs in FNAB-derived cell blocks was always concordant with the subtype determined in surgical material.

We demonstrated that biological marker determination in FNAB-derived cell blocks is feasible, and provides useful information and comparable results to those obtained with histological evaluation. Given the low cost of the procedure and its minimal impact on patients, we believe that cytological samples could be used as an alternative to tissue samples for early BC biomarker evaluation.