Notably, nodular structures within the appendiceal lumen can be indicative of malignant potential,[18] with these nodules representing coagulated mucin and granulation tissue formed due to cancer cell proliferation.[19] In summary, although appendiceal mucinous tumors concomitant with PMP are rare, their mucinous ascites present distinct ultrasound features that assist in identifying the appendiceal mucinous tumor as the primary lesion, thereby providing crucial ultrasonographic evidence for the diagnosis of PMP. Here, MUC5AC is linked to cancer.