Diagnosis of metachronous multiple lung adenocarcinoma at the cut-end by epidermal growth factor receptor mutation status discordance 4 years after sublobar resection for adenocarcinoma in situ: report of a case.

We report a case of metachronous multiple lung adenocarcinoma at the cut-end, diagnosed 4 years after sublobar resection for adenocarcinoma in situ (AIS), on the basis of discordance of epidermal growth factor receptor (EGFR) mutation status between the first and second tumor. The patient was an 81-year-old Japanese man, whose chest computer tomography (CT) scan showed mixed ground-glass opacity in the right upper lobe of the lung. Wedge resection was performed and a diagnosis of AIS, non-mucinous (18 × 14 mm), with a margin of 6 mm, was made. A tumor at the cut-end was seen on a CT scan 4 years later, and abnormal uptake was identified by fluorine-18 fluorodeoxyglucose-positron emission tomography. Right upper lobectomy and lymph node dissection were performed and the tumor was diagnosed as invasive adenocarcinoma, acinar predominant. Discordance of EGFR mutation status between the first tumor, harboring exon 19 deletion, and the second tumor, having an L858R point mutation in exon 21, revealed that the second tumor was metachronous multiple lung cancer. This case demonstrates the necessity of comparing EGFR mutation status between the first tumor and the second tumor at the cut-end.