Role of epidermal growth factor mutational status for distinction between recurrent lung cancer and second primary lung cancer: case report

INTRODUCTION: In a patient with previous radically treated lung adenocarcinoma, the detection of a new lung cancer raises the question whether recurrence or a second primary lung cancer is involved. Current criteria for differentiating multiple lung tumors lack a biologic and molecular basis and may lead to misclassification with impact on survival. OBJECTIVES: We report the case of a female patient with a recent diagnosis of lung adenocarcinoma and a previous lung adenocarcinoma submitted to curative surgical therapy 4 years before. As both lesions were resected, were of the same histologic subtype and presented the same immunohistochemistry profile; we decided to perform mutational analysis of the epidermal growth factor (EGFR) gene to differentiate between recurrence and second primary lung cancer. METHODS: The EGFR gene was screened for mutations in exons 18, 19, 20 and 21 using direct sequencing of polymerase chain reaction products in DNA obtained from paraffin preserved cells from both tumors. RESULTS: Mutational analysis of the EGFR gene, revealed different mutations in each tumor (both on exon 19) allowing the confirmation of the diagnosis of two metachronous primary lung cancers. CONCLUSIONS: In this patient, mutational analysis of the EGFR gene was superior to histologic and immunohistochemistry characterization in differentiating between recurrent lung cancer and second primary lung cancer; allowing confirmation of the diagnosis of two metachronous primary lung cancers.