Are heterogenous results of EGFR immunoreactivity in renal cell carcinoma related to non-standardised criteria for staining evaluation?

AIMS To assess whether heterogeneity of epidermal growth factor receptor (EGFR) immunoreactivity in renal cell carcinoma (RCC) is related to non-standardised criteria for staining evaluation. METHODS EGFR expression was investigated in 132 primary and 55 metastatic conventional RCCs using a tissue microarray technique. RESULTS Overall, membranous and/or cytoplasmic EGFR immunostaining was present in 123 of 132 (93%) primary and 49 of 53 (92%) metastatic RCCs, with extensive immunoreactivity (> 50% of tumour cells) in 110 of 132 (83%) primary tumours and 39 of 53 (73%) metastases. Cytoplasmic staining was associated with high tumour stage and high tumour grade. In addition, strong membranous staining (score 3+) prevailed in high grade RCCs. Cytoplasmic immunostaining was associated with an unfavourable prognosis, whereas overall (cytoplasmic and membranous) immunoreactivity and intensity of membranous staining were not. CONCLUSIONS Different methods of immunohistochemical evaluation led to different results, strengthening the need for standardisation, especially against a background of rapidly evolving EGFR targeted cancer treatment strategies.