[Clinicopathological features of early-stage lung adenocarcinomas with co-occurrence of MET exon 14 skipping mutation and gene amplification].

Objective: To investigate the abnormalities of mesenchymal-epithelial transition factor (MET) gene in early-stage lung adenocarcinomas and to provide genetic bases for related clinical studies. Methods: A total of 630 cases of formalin-fixed and paraffin-embedded lung adenocarcinoma specimens with ALK and EGFR double-negativities were collected at Peking Union Medical College Hospital, Beijing, China between July 2020 and April 2022. Forty-three stage Ⅰ-ⅢA tumors with MET exon 14 skipping mutation identified by reverse transcription droplet digital PCR (RT-ddPCR) were identified and then evaluated for MET amplification using fluorescence in situ hybridization (FISH). MET amplification was determined using the ratio of MET to chromosome 7 enumeration probe (CEP7) or the mean of MET gene copy number (GCN). Results: Among the 43 samples with MET exon 14 skipping mutation, MET amplification was detected in 9 cases (9/43, 20.93%), including 1 case of MET/CEP7 ≥2 and GCN ≥5 (1/9), 8 cases of GCN≥5 (8/9), as well as 10 cases with high level of CEP7 (7.00-9.72) which included 5 cases with MET amplification. There were no significant differences in clinicopathological features between the two subgroups of tumors which harbored MET exon 14 skipping mutation with MET amplification versus those without (P>0.05). Conclusions: Co-occurrence of MET exon 14 skipping mutation and MET amplification or high level of CEP7 is frequently observed in early-stage lung adenocarcinomas. The most common pattern of MET gene amplification is GCN ≥5.