Possible reasons for the lower exosomal PD-L1 values at the time-point of recurrence compared to the pre-therapuetic situation may be a reduced immune infiltrate in the recurrent tumour [24, 25] or a lower grade of differentiation of the usually more aggressive recurrent tumour compared to the primary, treatment-naïve tumour [26–29]. The gene discussed is CD274; the disease is neoplasm.