Liquid biopsy test reported actionable alterations in ARID1A gene...Nivolumab 3 mg/kg intravenously every 2 weeks was administered for 38 cycles....The patient was treated with immunotherapy, and showed a treatment response lasting for 19 months until a new metastasis appeared at the right deltoid muscle. Genomic analysis of a sample of this metastasis confirmed PD-L1 positivity of greater than 50% with CD8+ T cells expression and showed MSI with a deleterious c.298C>T (p.R100*) MLH1 gene mutation.