Background
Epidermal growth factor receptor (EGFR) overexpression (EGFR-H) is implicated in thyroid carcinoma disease progression, but the clinicopathologic significance of EGFR-H in tumors that harbor EGFR and/or BRAF(V600E) mutations is unknown.
Methods
Tissue microarrays from 81 patients who underwent thyroidectomies for carcinoma from 2002-2011 were scored for EGFR expression using immunohistochemistry (IHC). Somatic mutations in EGFR exons 19 and 21 and BRAF were analyzed. Correlations between EGFR IHC, EGFR, and BRAF(V600E) mutations and clinicopathologic features were assessed.
Results
EGFR-H was detected in 39.5% of carcinomas (n=32) from patients with papillary (PTC, 46.2%, n=18), follicular (29.6%, n=8), and anaplastic (ATC, 100.0%, n=6), but not medullary (0.0%, n=9) thyroid carcinoma. BRAF(V600E) mutations were identified in 22.2% of carcinomas (n=18, 15 PTCs and 3 ATCs). No somatic EGFR mutations were detected in any subtype. On PTC univariate analysis, EGFR-H correlated with increasing stage, extrathyroidal extension (ETE), tumor capsule invasion (TCI), adverse pathologic features (APF: any demonstration of ETE, TCI, lymph-vascular invasion, lymph node metastases, and/or distant metastases), and BRAF(V600E) mutations. On multivariate analysis, EGFR-H correlated with BRAF(V600E) mutations. In BRAF wild-type (BRAF-WT) PTCs, the correlation between EGFR-H and APF approached statistical significance (p=0.065).
Conclusions
EGFR-H may be an important biomarker for aggressive PTCs, particularly in BRAF-WT PTCs. Despite EGFR-H in PTC, FTC, and ATC by immunohistochemistry, somatic EGFR mutations are absent. Therefore, future investigations of EGFR should consider histologic and immunohistochemical methods in addition to molecular profiling of thyroid carcinomas. This multimodality approach is particularly important for future clinical trials testing anti-EGFR therapy.