Molecular diagnostics of a single multifocal non-small cell lung cancer case using targeted next generation sequencing

Histological and molecular subtyping of non-small cell lung cancer (NSCLC) is important for predicting survival and drug response in these patients. Up to 8 % of NSCLC are multifocal and these tumor foci are often clonally related. Multiple foci can however also represent different primary tumors, with prognostic and therapeutic consequences. We describe a patient with multifocal NSCLC from which we obtained tissue from two separate lesions. With routine conventional molecular determinations, the clonal relationship between the two lesions was determined. In addition, targeted next generation sequencing with the Ion Torrent Personal Genome Machine (PGM) was performed to explore the accuracy and additional value of this relatively new technique. The two tumors of this patient showed different activating epidermal growth factor receptor (EGFR) mutations, EGFR amplification status, TP53 mutation status, and loss of heterozygosity patterns. With the PGM, all conventional detected mutations were confirmed, and an additional variant of unknown significance in ATM was detected in one of the tumors. The multifocal NSCLC of this patient represents two unrelated primary tumors. Our results suggest that multifocal NSCLC should be considered as potentially multiple primary tumors. As the presence of activating EGFR mutations has important therapeutic consequences, EGFR testing should be performed on all tumor foci present. In the present case, targeted next generation sequencing using the PGM appeared to be accurate and comparable with conventional molecular determinations. However, the application of the PGM in routine pathology molecular diagnostics needs validation in larger series of cases.

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