Consistently, the protein abundance of Notch1 intracellular domain (NICD), the major activator of canonical Notch signaling pathway, as well as Notch effector HES1, were markedly increased in KLN mucinous tumors relative to non‐mucinous tumors, as evidenced by IHC staining and statistical analyses (Fig 4B–D). Here, HES1 is linked to mucinous neoplasm.