Epidermal Growth Factor Mutation as a Diagnostic and Therapeutic Target in Metastatic Poorly Differentiated Thyroid Carcinoma: A Case Report and Review of the Literature

Poorly differentiated cancers are a diagnostic and therapeutic challenge in oncology. New therapies are needed for patients with poorly differentiated thyroid carcinoma (PDTC) or anaplastic thyroid cancer, as these patients often present with advanced disease and effective systemic treatment options are currently limited. Epidermal growth factor (EGFR) mutations may occur in PDTC more often than previously thought. However, there are fewer than 6 cases reported in the literature where EGFR tyrosine kinase inhibitors (TKIs) (such as erlotinib or gefitinib) were used to target EGFR mutations in PDTC. Here, we present the case of a 79-year-old male with metastatic PDTC with an EGFR mutation who responded to treatment with the selective EGFR TKI erlotinib, with a progression-free survival of more than 11 months. A lung primary rather than a thyroid primary was initially detected. We suggest that the EGFR status should be analysed at diagnosis in any patient with a poorly differentiated tumour. The presence of an EGFR mutation may provide an effective therapeutic pathway for these patients. This pathway requires further investigation and consideration in the future.Key words: Metastatic thyroid carcinoma, Poorly differentiated thyroid carcinoma, Targeted therapy, Epidermal growth factor mutation, Tyrosine kinase inhibitors, Erlotinib, Intratumoural heterogeneity, Poorly differentiated carcinoma