Intralesional Methotrexate Injection for The Treatment of Epithelial Crateriform Tumor

Intralesional methotrexate (IL-MTX) is a therapeutic method to treat Keratoacanthoma (KA), which is a representative tumor of various epithelial crateriform tumors (ECTs). However, not all of ECTs are responsive to IL-MTX treatment. We retrospectively reviewed 12 patients who received IL-MTX for the treatment of ECTs between 2015 to 2022. The effectiveness was evaluated in terms of size reduction and divided into 3 groups : Complete response (CR), partial response (PR), and no response (NR). Among twelve patients with ECT, eight patients reached to CR and four patients showed 3 NR and 1 PR individually. Nine patients underwent skin biopsy before IL-MTX treatment. Five were well differentiated squamous cell carcinoma (SCC), 2 were KA, and 2 were moderate to poorly differentiated SCC. All patients with biopsy confirmed KA experienced CR without recurrence. 60% of well differentiated SCC showed CR but 40% showed NR. In two patients with moderate to poorly differentiated SCC, one patient experienced pathological CR, and the other patient experienced PR. IL-MTX treatment can be an effective conservative therapeutic option for patients with biopsy confirmed KA and well differentiated SCC. In addition, pre-surgical IL-MTX can also be an option for SCC with unfavorable pathologic type.