EGFR and Oral ulcer: However, the clinical application of EGFR ectodomain-targeted therapy has been limited by the prevalence of EGFR in normal tissues, such as skin and endothelium of blood vessels, which raises the concern for on-target, off-tumor toxicity,26 including oral mucositis, oral ulcer, gastrointestinal hemorrhage, desquamation, and pruritus.