Diagnosis of synchronous primary lung adenocarcinomas based on epidermal growth factor (EGFR) gene status: A case report.

The diagnosis of multiple primary lung cancer is sometimes difficult when multiple lung tumors with the same histologic type are identified. We now present a case of synchronous double primary lung adenocarcinomas (one in the right upper lobe and another in the right middle lobe) diagnosed based on mutational analysis of the epidermal growth factor receptor (EGFR) gene, although clinico-pathological findings suggested the diagnosis of intrapulmonary metastasis. After complete resection, pathological sections revealed the similar pathological features of two adenocarcinomas and unexpected subcarinal nodal metastasis. As the L858R mutation within exon 21 of the EGFR gene was identified in the middle-lobe tumor and the subcarinal node but not in the upper-lobe tumor, we diagnosed as double primary cancers. Local mediastinal recurrence after operation has been well-controlled with administration of gefitinib, a EGFR-tyrosine kinase inhibitor, and mutational analysis of the EGFR gene provided important information not only in the diagnosis of double primary cancers but also in decision-making of selection of chemotherapeutic agent.