Concurrent high-grade appendiceal mucinous neoplasm and adenocarcinoma: a unique case report and literature review.

Appendiceal neoplasms (ANs) are rare and often mimic acute appendicitis, complicating timely diagnosis. We report a unique case of a 57-year-old male presenting with right lower quadrant pain, found on imaging to have a ruptured appendiceal mucocele. He underwent open right hemicolectomy, and histopathology revealed concurrent moderately differentiated mucinous adenocarcinoma arising within a high-grade appendiceal mucinous neoplasm-the first such case documented in the literature. This case underscores the need for early detection, proper surgery, and long-term follow-up in managing rare concurrent appendiceal tumors.