In 2016, Kuklinski et al. assessed the PD-L1 expression within 16 skin biopsies of patients with diverse mastocytosis types, including diffuse CM, solitary mastocytoma, and SM involvement (mastocytosis in skin) and found strong and diffuse PD-L1 staining within all mastocytosis specimens, regardless of the subtype [14]. The gene discussed is CD274; the disease is cutaneous mastocytosis.