Immunochemistry for oestrogen receptor, progesterone receptor and HER2 on cell blocks in primary breast carcinoma

Steroid receptors and human epidermal growth receptor 2 (HER2) have been used for predicting response to treatment in breast cancers. Fine needle aspiration cytology can provide highly cellular material and can be used for such analysis. The present study was undertaken to assess the reliability of oestrogen and progesterone receptor (ER, PR) status and HER2 as demonstrated by immunochemistry (IHC) on cell blocks from breast carcinoma cases, in comparison with histological sections.

IHC for ER, PR and HER2 was performed on cell blocks and their corresponding tissue sections of 50 primary pre-chemotherapy breast carcinomas. Positivity for ER and PR was scored according to the Allred scoring system. Strong membranous positivity in more than 30% of tumour cells was considered positive for HER2. The tumours were classified as luminal A, luminal B, HER2-over-expressing and triple negative on the basis of ER, PR and HER2 status and results on cell blocks compared with histological sections.

Correlation between immunostaining on cell blocks and the corresponding tumour tissues revealed a concordance rate for ER, PR and HER2 of 90% [Correlation coefficient (r) = 0.79], 94% (r = 0.86) and 90% (r = 0.76), respectively. Including five cases in which cell blocks were either ER or PR positive, 43/50 cases (86.0%) could be correctly classified on cell block immunostaining alone. The main reasons for seven discordant cases included technical errors (sampling error and staining error) and interpretational error in HER2 evaluation on cell blocks; the core biopsy was inadequate in one, and apparently false negative for HER2 in another.

Cell blocks are useful in the assessment of hormone receptor status and HER2 by IHC, especially in cases of locally advanced breast cancer for planning neoadjuvant chemotherapy. It is highly recommended to have good quality cell blocks and quality control of their interpretation.