Aim: We describe a case of an advanced disease non-small-cell lung cancer patient with low PD-L1 expression, but high tumor mutation burden (35 muts/Mb) who developed immune-related hypothyroidism and achieved subsequent partial response, while on clinical trial (NCT03382912) with nivolumab and PEGylated IL-10 (Pegilodecakin, ARMO BioSciences/Eli Lilly and Company, IN, USA). Results/conclusion: Results suggest positive antitumor activity to combination IL-10/nivolumab despite low PD-L1 expression but in likely relationship to high tumor mutation burden and in association with immune-mediated thyroid dysfunction in this case.