John M. Skaugen, MD, Tim D. Oury, MD, PhD, Yuri E. Nikiforov, MD, PhD
The patient was an elderly man in his 80s who presented with dyspnea, fatigue, and subacute weight loss. Imaging identified a large left lower lobe mass with mediastinal lymphadenopathy. A CT-guided biopsy was performed, which identified a poorly differentiated adenocarcinoma (Figure 1) which was positive for CK7 and TTF-1 but negative for CK5/6 and p40, consistent with lung origin. Ancillary testing was performed, and the tumor cells were positive for PD-L1 (TPS 50%) and negative for ALK by immunohistochemistry (IHC). Fluorescence in-situ hybridization (FISH) was negative for ALK rearrangement (other targets failed). Oncomine next generation sequencing (NGS) was also performed, which identified a TP53 mutation, MET splice site mutation near codon D981, and "fusion" adjoining exons 13 and 15 of MET (Figures 2 and 3).
What is the diagnosis?