Additionally, testing for microsatellite instability (MSI), mismatch repair (MMR) status, tumour mutational burden (TMB), and other relevant markers, such as folate receptor alpha (FRα), B-rapidly accelerated fibrosarcoma (BRAF) gene alternation, neurotrophic tyrosine receptor kinase (NTRK) and rearranged during transfection (RET) gene alternation, is crucial if these were not included in previous assessments. The gene discussed is RET; the disease is fibrosarcoma.