Pseudomyxoma peritonei from independent primary ovarian and appendiceal tumors: a case report

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Pseudomyxoma peritonei (PMP), which involves both the ovaries and appendix, is usually attributed to an appendiceal primary tumor with secondary involvement. However, rare cases may present with synchronous, independent mucinous primaries. Distinguishing between these entities is important because staging, treatment, prognosis, and follow-up may differ according to the primary site. An 83-year-old woman presented with abdominal distension and ascites incidentally discovered during an evaluation for traumatic intracranial hemorrhage. Computed tomography revealed large-volume ascites, a large multilocular cystic mass arising from the left ovary, and a dilated appendix. Diagnostic laparoscopy confirmed the presence of gelatinous ascites, which was consistent with PMP. Histopathological examination revealed ovarian mucinous carcinoma and appendiceal mucinous neoplasms. Immunohistochemistry showed discordant profiles for ovarian (cytokeratin [CK]-7+/paired box 8 [PAX8]+/CK-20-/caudal-type homeobox 2 [CDX-2]-) and appendiceal (CK-20+/CDX-2+/CK-7-/PAX8-) lesions. Peritoneal tumor cells expressed CK-7 but lacked PAX8, CK-20, and CDX-2 expression, supporting an ovarian-type immunophenotype of the peritoneal disease. The patient underwent diagnostic laparoscopy with left salpingo-oophorectomy and removal of the gelatinous ascites. Two cycles of paclitaxel and carboplatin were administered before interval cytoreductive surgery because of advanced disease, arrhythmia, and poor tolerance to prolonged surgery. Complete cytoreduction was achieved through total hysterectomy, right salpingo-oophorectomy, appendectomy, total parietal peritonectomy, omentectomy, cholecystectomy, splenectomy, and the removal of visible disease, followed by carboplatin monotherapy. Complete cytoreduction was achieved, and the patient completed adjuvant carboplatin therapy without grade 3 or higher adverse effects. The patient remained disease-free for 6 months after the completion of chemotherapy.