PD-L1 expression in tumour microenvironment supports the rationale for immune checkpoint blockade in classic Kaposi's sarcoma

Kaposi's sarcoma (KS), a rare human herpesvirus type 8 (HHV8)-associated lymphangioproliferative disorder, is usually skin-limited and slowly progressing.1 However, in the rare cases of locally aggressive or visceral KS refractory to chemotherapy, programmed death-1/programmed death-ligand 1 (PD-1/PD-L1) blockers, a class of immune-checkpoint inhibitors which acts via the circumvention of tumour immune escape and has shown durable anti-tumour effects in specific subsets of patients with different solid tumours, have been invoked as a promising therapy.