About 3⁄4 of virus-negative MCC show alterations in Notch, thus Notch1 mutations are observed in up to 90% of MCC cases (Goh et al. 2016; Panelos J et al. 2009; Wardhani et al. 2019; Brazel et al. 2023). Here, NOTCH1 is linked to Merkel cell skin cancer.