Two Unusual Mutations in the Epidermal Growth Factor Receptor Gene in a Patient With Lung Adenocarcinoma

Adenocarcinoma (ADC) of the lung is the most frequent pathology corresponding to non-small cell lung cancer (NSCLC). The advent of target therapy and the discovery of drugs that block signaling pathways related to cellular events involved in the progression of the disease have led to a better prognosis in cases of ADC. Some of the targeted therapy focuses on the blockade of epidermal growth factor receptor (EGFR), targeting mutations in exon 19 and 21, with favorable clinical outcomes. However, there is limited evidence with respect to unusual mutations as in exon 18 (g719x) and 20 (s768). In this report, we present a case of a 65-year-old female with two unusual mutations in the EGFR gene, in exon 18 (g719x) and 20 (s768i), without central nervous system (CNS) involvement; these mutations are typically resistant to standard therapy. We decided to administer osimertinib because of its favorable toxicity profile and with a view to preventing future CNS relapse.