In keeping with dMMR in other solid tumours, most dMMR PCa demonstrate increased infiltration of CD8+ and CD4+ T cells, with increased expression of the immune checkpoint PD-L1, although notably a significant proportion of dMMR PCa (approximately 45% based on a small study of nine cases) do not demonstrate increased lymphocytic infiltration, potentially accounting for lack of response to ICB in some cases. Here, CD4 is linked to posterior cortical atrophy.