ERBB3 and mucinous adenocarcinoma: An alternate, intriguing biomarker for anti-ErbB3 drugs would be activating NRG1 fusions, found to be oncogenic drivers in approximately one-third of invasive mucinous adenocarcinomas of the lung, however only present in 0.5% of HNSCC, thus making them impractical for patient selection in HNSCC-specific trials [33].