Appendiceal mucinous neoplasm mimics ovarian tumors: Challenges for preoperative and intraoperative diagnosis and clinical implication.

OBJECTIVE: The aim of this study was to investigate the clinicopathological characteristics of appendiceal mucinous neoplasm that had been preoperatively misdiagnosed as a mucinous ovarian tumor and to discuss the clinical impacts of misdiagnosis.

METHODS: Seventy-eight patients with a final pathologic diagnosis of appendiceal mucinous neoplasm during a 10-year period were retrospectively reviewed. All patients were diagnosed with ovarian tumor before treatment. A univariate analysis was performed to evaluate predictors of the diagnostic accuracy of a frozen section.

RESULTS: The patients' median age was 61 years (range, 21-82 years), and most were diagnosed as low-grade appendiceal mucinous neoplasm (LAMN) (84.62%). The diagnostic concordance between the frozen section and the final pathology was 56.92%. The most consistent diagnosis was LAMN (64.14%). Univariate analysis indicated that maximal diameter of the ovarian tumor (unilateral), laterality of the ovarian tumors (unilateral or bilateral), and frozen section site (appendix or extra-appendix) significantly correlated with the accuracy of frozen section diagnosis (all p < 0.05). Although the diagnostic discordance between the frozen section and the final pathology was 43.08%, only one patient was clinically impacted because of suboptimal surgery.

CONCLUSION: Appendiceal mucinous neoplasm should be considered as a differential diagnosis of pelvic mass in women. For patients who do not require fertility-sparing surgery, excision and frozen section of the bilateral ovaries and appendix regardless of the appearance of the appendix might improve the diagnosis. For older patients with peritoneal dissemination, appropriate cytoreductive surgery is recommended to reduce the clinical impact of misdiagnosis.