Successful Treatment of Metastatic Primary Cutaneous Adnexal Carcinoma With a PD-1 Inhibitor.

Standard of care treatment for metastatic cutaneous adnexal carcinomas is not well established. In this case report, we highlight the successful use of anti-programmed cell death protein 1 (anti-PD-1) therapy in treating a patient with low tumor mutation burden, microsatellite stable, high programmed death-ligand 1 (PD-L1) gene expression, metastatic primary cutaneous adnexal carcinoma with significant radiographic, and circulating tumor DNA response with durable benefit. Immune checkpoint inhibitors hold promise as a future treatment option in rare instances of metastatic disease from primary skin adnexal carcinoma. Further studies are needed to identify better immune checkpoint inhibitor predictive biomarkers for rare, advanced-stage non-melanoma skin cancers.