An uncommon multimodal management approach for low-grade appendiceal mucinous neoplasm with pseudomyxoma peritonei and mucinous borderline ovarian tumor.

Introduction and importance: Low-grade appendiceal mucinous neoplasm (LAMN) is a rare epithelial tumor characterized by mucin production and potential dissemination into the peritoneal cavity, resulting in pseudomyxoma peritonei (PMP). The coexistence of LAMN with a mucinous borderline ovarian tumor (MBOT) represents a complex and exceedingly rare clinical scenario. Unlike the main introduction, this abstract focuses on the clinical and therapeutic significance rather than epidemiology. There are no standardized treatment protocols for synchronous LAMN with MBOT; hence, individualized management is essential. This report highlights an uncommon multimodal strategy combining cytoreductive surgery (CRS), modified FOLFIRINOX chemotherapy incorporating irinotecan, and planned second-look surgery with hyperthermic intraperitoneal chemotherapy (HIPEC). Case presentation: A 44-year-old woman presented with abdominal distension. Imaging revealed diffuse mucinous peritoneal deposits, thickened appendix, and multilocular ovarian cyst. Preoperative CA-125 was 142 U/mL, and CA 19-9 was 280 U/mL. CRS including appendectomy, right hemicolectomy, omentectomy, and bilateral salpingo-oophorectomy was performed. Histopathology confirmed LAMN with PMP and MBOT. The Peritoneal Cancer Index at primary surgery was 18. A multidisciplinary team recommended systemic chemotherapy with modified FOLFIRINOX including irinotecan before second-look HIPEC. The patient tolerated the regimen well. Clinical discussion: This case underscores an emerging role of irinotecan-based chemotherapy as part of a tailored multimodal treatment for low-grade mucinous neoplasms, especially in resource-constrained environments. Conclusion: The patient remained disease-free at 1-year follow-up, highlighting the potential effectiveness and practicality of irinotecan-based regimens as part of an individualized management strategy for low-grade mucinous neoplasms.