For example, epidermal growth factor receptor (EGFR) monoclonal antibodies (cetuximab) and immune checkpoint inhibitors (ICI), such as pembrolizumab or nivolumab, produce variable manifestations, including lichenoid mucositis (mixed white striations, erythema, and/or ulcerations), vesiculobullous features, erythema multiforme, or Stevens–Johnson syndrome/toxic epidermal necrolysis (SJS/TEN) [11,12,13]. The gene discussed is EGFR; the disease is erythema multiforme.