O’Connell et al. investigated the mucin composition of PMP, which is principally made of MUC2 and MUC5AC and revealed that while MUC2 was more abundant in PMP, but also in appendiceal mucinous tumors and normal digestive tissue, MUC5AC was predominant in mucinous ovarian primitive tumors, suggesting that mucin composition could help to distinguish the origin of PMP [26, 27]. The gene discussed is MUC5AC; the disease is mucinous neoplasm.