Targeted DNA sequencing for assessing clonality in multiple lung tumors: A new approach to an old dilemma

The differential diagnosis between multiple primary lung cancer (MPLC) and advanced lung cancer has traditionally relied on conventional radiology and pathology. However, the outcomes of traditional diagnostic workup are often limited, and staging is uncertain. Increasing evidence suggests that next-generation sequencing (NGS) techniques offer the possibility of comparing multiple tumors on a genomic level.

The objective of this study is to assess the clinical impact utility of targeted sequencing in patients presenting with multiple synchronous or metachronous lung tumors.

We describe the diagnostic workup conducted in a patient with three lung tumors, where we used a targeted 50-gene DNA sequencing panel (Ion AmpliSeq TM Cancer Hotspot Panel v2) to assess clonality and establish an accurate lung adenocarcinoma stage. Positive results were confirmed by pyrosequencing or Sanger sequencing.

Three surgically resected lung tumors were submitted for targeted sequencing. The tumor from the upper right lobe was positive for a TP53 c.659A > G mutation and native for KRAS. The tumor from the upper left lobe was positive for TP53 c.725G > T and KRAS c.35G > T mutations. The tumor from the lower left lobe was positive for TP53 c.1024C > T and KRAS C.34G > T mutations. Results and reviewed literature in the field support the diagnosis of MPLC instead of a single advanced lung cancer.

Targeted DNA sequencing significantly increases diagnostic accuracy in patients with multiple lung tumors. NGS panels should be available for patients presenting with multiple lung tumors.