Because only a few studies have been published on this topic, we have read with great interest the article of Lohinai et al. titled, "Distinct Epidemiology and Clinical Consequence of Classic versus Rare EGFR Mutations in Lung Adenocarcinoma." 1 The authors compare the epidemiology and clinical consequence of classical and rare epidermal growth factor receptor gene (EGFR) mutations in a cohort of Hungarian patients with lung adenocarcinoma. They defined classical EGFR mutations as the combination of the L858R point mutation in exon 21 and exon 19 microdeletions, rare EGFR mutations as nonclassical mutation in the tyrosine kinase-coding region (exons 18-21) where amino acid change occurs, and synonymous EGFR mutations as nucleotide changes without protein alterations.In their article, Lohinai et al. reported that classical and rare nonsynonymous EGFR mutations were identified in 5% and 6% of patients, respectively. This finding is quite surprising for several reasons. First, the incidence of rare EGFR mutations in this study is much higher than in similar studies of whites (0.8%-4.4%). [2][3][4] Lohinai et al. justified this high rate of rare EGFR mutations by the facts that exon 20 sequencing was also performed in three-fourths of patients and 40% of all patients with Kirsten rat sarcoma viral oncogene homolog (KRAS) mutations underwent EGFR analysis as well. In our opinion, these arguments cannot fully explain the high rate of rare EGFR mutation because most of the recent studies in whites that have reported the frequency of EGFR mutation subtypes have also included exon 20 analysis 2-4 and, on the other hand, only three patients (< 0.4%) with a concomitant KRAS mutation and rare EGFR mutations were found in the present study.Second, the fact that the proportion of rare EGFR mutations is higher than that of classical ones, as found in this series, seems inadequate by definition. Indeed, in studies of both whites and Asians, it has been reported that about 90% of all lung adenocarcinoma-associated EGFR mutations are classical ones whereas the proportion of rare EGFR mutations does not usually exceed 10% to 15%. [3][4][5] Of note, in our retrospective study that was recently published in this journal, the rate of rare EGFR mutations (exon 20 analysis was also performed) was 10% of all mutations. 6 Finally, we agree with the authors' statement with regard to the fact that some of their results need to be confirmed in a prospective setting because in any retrospective study, some sources of bias cannot be ruled out.