LAUSR

Background Synchronous multiple primary lung cancers (sMPLC) are rare forms of lung cancer, and their diagnosis remains as a significant challenge. Distinguishing sMPLC from advanced disease is important as their prognoses and therapeutic management vary dramatically. Case presentation The patient was a 56-year-old Chinese male who exhibited six synchronous invasive adenocarcinomas at diagnosis [T2(6)N0M0], and who achieved durable clinical benefit under adjuvant chemotherapy for 41 months following wedge resection and lobectomy. Whole-exome sequencing revealed that two lesions (L4 and L6) in the left upper lobe of the patient’s lung shared 28 nonsynonymous mutations; thus, suggesting that the lesions may have arisen from a common ancestor at the early stages of tumorigenesis, and spread into distinct histologic subtypes. Moreover, while L5 was in the same lobe as L4 and L6, it represented a distinct lineage as it did not share any mutations with other lesions. Notably, the BRAF V600E oncogenic mutation was exclusive to L5. In addition, the KRAS G12C mutation was identified in three lesions (L1-L3) located in the right lung, which may have resulted from convergent evolution. Conclusion We report a patient with six synchronous invasive adenocarcinomas who demonstrated durable clinical benefits under adjuvant chemotherapy following surgical treatment. While cancer staging is one of the many challenges associated with sMPLC, the data generated through next-generation sequencing can provide information on lesion origins, and thus, advance the era of precision medicine.