Aims: To follow and compare immunohistochemical expression of epidermal growth factor receptor (EGFR) in tumour cells during the entire natural history of colonic carcinoma, from primary tumour to paired lymph node and sequentially resected liver metastases; and to test interobserver reproducibility of EGFR analysis.
Methods and results: Forty patients had resection of colonic adenocarcinoma (27 with metastatic lymph nodes) and at least one partial hepatectomy (PH) for liver metastases; a second and a third PH were performed, respectively, in 14 and three patients; seven patients had tumour liver biopsy. EGFR immunohistochemistry (n = 130) was analysed independently by two pathologists. EGFR expression (membranous staining detected in > or = 1% of tumour cells) was detected in 38/40 colonic carcinomas, 23/26 lymph nodes and 51/64 liver metastases. Both primary tumours and related metastases were EGFR+ in 28 patients (73%). Discrepancies were found in EGFR status between liver and lymph node (23%) and among the different liver samples (31%). Interobserver agreement was very good (intraclass correlation coefficients of 0.81, 0.91 and 0.85, respectively, for interpretation of staining in colon, lymph node and liver metastases).
Conclusions: Since immunohistochemical detection of EGFR remains a prerequisite for EGFR-targeted therapy eligibility, different tumour samples should be tested to allow every patient a chance to take advantage of this treatment.