Immune cells in mesothelioma microenvironment simplistic marker of response to nivolumab plus ipilimumab?

•Nivolumab plus ipilimumab is an effective treatment for malignant pleural mesothelioma.•Biopsies before nivolumab plus ipilimumab treatment show a higher cell density of CD4+, CD8+, FoxP3+ and PD-1+ cells in responding patients.•Biopsies during treatment with checkpoint inhibitors do not show a significant change when compared to baseline.•Larger trials are needed with a more detailed analysis of mesothelioma tumor microenvironment.