In a study using targeted NGS of 104 cancer‐related genes on 197 MPN patients to examine clonal evolution over time 31, approximately 10% of patients had no mutation detectable in any of the genes analysed and 54% had mutations only in JAK2 V617F or CALR. These patients were found to have the most favourable prognosis and the lowest risk of disease progression. The gene discussed is CALR; the disease is myeloproliferative disorder.