Multiple primary lung adenocarcinomas pre‐operatively diagnosed by discordant epidermal growth factor receptor mutations

A 49‐year‐old woman with an abnormal shadow on her chest X‐ray visited our hospital. Chest computed tomography revealed a 13‐mm diameter nodule in S9 on the right and a 47‐mm diameter mass in segment (S) 1 + 2 on the left. She underwent transbronchial biopsy, which revealed that both tumours had the same histology of papillary adenocarcinoma. The indications of radical surgery differ between metastatic and multiple primary cancers; however, the epidermal growth factor receptor mutation screenings turned out to be discordant, with exon 19 deletion in the right and exon 21 L858R mutation in the left tumour. This is the first case report of a pre‐operative diagnosis of multiple primary adenocarcinomas eligible for radical surgery. Thorough assessment is recommended in cases wherein the differential diagnosis is considered to be a factor for surgical indication. Genetic screening provides additional diagnostic information despite the presence of tumours manifesting the same histological type.