Identification of a Novel MCAM

Abstract

Background RAS pathway alterations are major oncogenic drivers in non-small cell lung cancer (NSCLC), most commonly through KRAS point mutations and activating alterations in receptor tyrosine kinases like EGFR. We report a novel oncogenic fusion involving RASGRF1, a RAS-activating guanine exchange factor (GEF). Case presentation Awoman in her 70s, never-smoker, presented with E.coli bacteraemia and was found to have a right-sided pleural effusion. Pleural aspiration confirmed metastatic adenocarcinoma. CT and PET imaging showed no detectable lung or extrapulmonary primary. TTF-1 positivity suggested a lung primary. ctDNA testing did not identify any clinically actionable mutation. Targeted tissue DNA sequencing using the RMH200 panel demonstrated no pathogenic variants. Reflex RNAbased sequencing detected an in-frame MCAM