Identification of Actionable Gene Variants in Pulmonary Large-Cell Neuroendocrine Carcinoma: A Real-World Analysis of a Polish Cohort.

Pulmonary large-cell neuroendocrine carcinoma (LCNEC) is a rare lung malignancy characterized by an aggressive clinical course and an unfavorable prognosis. Next-generation sequencing (NGS) has revealed that LCNECs exhibit molecular features resembling either small-cell lung carcinoma (SCLC-like LCNEC) or non-small cell lung carcinoma (NSCLC-like LCNEC). This study aimed to characterize the incidence of actionable gene variants in a retrospective cohort of LCNEC patients using a targeted NGS approach. Microscopic diagnosis was established according to the 2021 World Health Organization (WHO) classification using a standard immunohistochemical (IHC) panel. In total, 216 LCNEC tumor samples were analyzed for molecular variants in 17 genes using the RNA-based Archer FusionPlex Lung NGS assay (Integrated DNA Technologies, USA) and the MiSeq platform (Illumina, USA)-an algorithm utilized for routine NSCLC diagnosis. Overall, 46 variants were identified in 46/216 (21.3%) tumor samples, with 28/216 (13%) LCNECs harboring at least one actionable molecular variant potentially targetable by registered or investigational agents. KRAS variants (5%; including G12C at 2%) and PIK3CA variants (5%) were the most prevalent, followed by RET single-nucleotide variants (3%), uncommon EGFR variants (1%), and BRAF class II and III variants (<1%). Notably, no classical EGFR exon 18-21 mutations nor ALK, FGFR1/2/3, or ROS1 alterations (mutations or fusions) were detected, despite the technical capability of the assay to identify such variants. A novel in-frame gene fusion (TMEM79::NTRK1) was identified in a single tumor sample (0.5%). Our results confirm that LCNECs harbor potentially targetable alterations in KRAS, PIK3CA, RET, BRAF, and NTRK1, albeit at lower frequencies than those typically observed in NSCLC.