PD-1 and PD-L1 expression in Kaposi sarcoma: A comparative study according to the pathological stage and clinical characteristics.

BACKGROUND: Kaposi sarcoma (KS) is a mesenchymal tumor with distinct histopathological features according to stage of progression. Programmed death-1 (PD-1) and its ligand PD-L1 play major roles in the immune escape strategy of tumors.

OBJECTIVES: This study evaluated expression of PD-1 and PD-L1 in various stages of KS and investigated associations between their expression and clinical characteristics.

METHODS: Fifty cases with histopathologically diagnosed KS were classified as early or late stage. These specimens were stained with anti-PD-1 and anti-PD-L1 antibodies. The extent of expression in the intratumoral and peritumoral areas was judged by two dermatopathologists.

RESULTS: PD-1 and PD-L1 were expressed in 72.2% (13/18) and 11.1% (2/18) of early-stage cases, respectively, compared with 43.8% (14/32) and 28.1% (9/32) of late-stage cases, respectively. At the late stage, PD-1 expression was significantly higher in the peritumoral area than in the intratumoral area (P = 0.001). PD-1 expression in the intratumoral area was significantly higher at the early stage than at the late stage (P = 0.013). PD-L1 expression in the peritumoral area was significantly higher at the late stage than at the early stage (P = 0.038).

CONCLUSIONS: The pattern of PD-1 and PD-L1 expression differs according to the stage of KS, but is unaffected by clinical variables.