LAUSR

BACKGROUND Solitary large keratoacanthomas (KAs) of the head and neck present a management dilemma, as no reliable means to predict the clinical course is available. Although typically considered a low-grade tumor, KAs are reported to invade/metastasize, prompting more aggressive treatment. There is little published regarding factors that predict when a KA behaves more like an aggressive squamous cell carcinoma (SCC). OBJECTIVE To study the clinical and pathologic features of large solitary head and neck KAs and assess response to intralesional methotrexate (IL-MTX) as well as predictors of clinical course. MATERIALS AND METHODS An observation study of 14 patients with large solitary head and neck KAs were treated with IL-MTX and then excised by Mohs micrographic surgery (MMS) at a later time point. Clinical presentation, treatment, response, and pathology were recorded. Features of classic KAs were compared with those with an aggressive SCC course. RESULTS Ten of fourteen lesions responded with necrosis, a decrease in size and/or pain, and histological clearance on MMS. However, 4/14 lesions continued to have progression despite IL-MTX therapy. These showed persistent pain, perineural invasion, moderate/poor differentiation, and an infiltrative growth. LIMITATIONS Small sample size. CONCLUSION Significant pain, or continued growth may suggest an underlying aggressive SCC in clinically classic large KAs. In these cases, surgical management with assessment for high-risk tumor features is recommended.