Anaplastic Classic Kaposi Sarcoma: PD-L1 Expression and Response to Immunotherapy: A Case Report and Review of the Literature.

Anaplastic classic Kaposi sarcoma (CKS) is an extremely rare pathologic variant of CKS characterized by high aggressiveness and poor prognosis. We report the clinical course of this malignant histologic form in an otherwise healthy 67-year-old male from Apulia in Southern Italy. The anaplastic progression arose during a long history of CKS and developed after multiple local and systemic treatments. The extremely aggressive and chemorefractory nature of the disease dictated amputation of a lower limb and, later, surgery for metastatic pulmonary involvement. At subsequent relapse, therapy with the anti-PD-1 inhibitor pembrolizumab was started. The immunotherapy was selected based on the PD-L1 expression in the tumor and tumor microenvironment. Remarkably, PD-1 blockade induced a complete and durable response in the patient, with a disease-free survival that has exceeded 18 months, and follow-up is still ongoing.