Patients with these MMR-deficient cancers are described as having abundant CD8+ cytotoxic T-cell infiltrate [7] and are often linked to more “favourable” tumor-related features, namely the presence of a pushing tumor border configuration, the presence of a distinctive band of peritumoral lymphocytic inflammation and little tumor budding, the latter a histomorphological hallmark of epithelial mesenchymal transition [8]. The gene discussed is CD8A; the disease is neoplasm.