Low-Grade Appendiceal Mucinous Neoplasm With Discontinuous Mucin Infiltration Into the Cecal Wall: A Case Report.

Low-grade appendiceal mucinous neoplasm (LAMN) can lead to intraperitoneal dissemination and subsequent pseudomyxoma peritonei (PMP). Therefore, achieving complete resection, typically by appendectomy, is considered important for curative treatment. We report a case in which discontinuous mucin infiltration into the cecal wall was identified only after secondary resection, providing insight into the extent of surgical resection. To the best of our knowledge, such cases appear to be rare, with limited reports in the literature. A 60-year-old female was incidentally found to have an enlarged appendix during evaluation for pneumonia. She underwent a laparoscopic appendectomy, and histopathological examination led to a diagnosis of LAMN. Based on the pathological findings, additional laparoscopic ileocecal resection was recommended, and the patient provided informed consent. Histological examination of the resected specimen revealed discontinuous acellular mucin infiltration limited to the muscularis propria of the cecal wall, which had not been detected preoperatively or intraoperatively. Surgical margins were negative, and no epithelial components were identified. No recurrence was observed during a two-year follow-up period. LAMN requires complete resection to reduce the risk of progression to PMP, which is associated with a poorer prognosis. Lymph node metastasis is rare, and limited resection is generally considered sufficient. However, in the present case, discontinuous mucin infiltration was identified within the cecal wall despite negative surgical margins. This finding highlights the potential limitation of preoperative imaging and intraoperative assessment in detecting such lesions. One possible speculative mechanism is increased intraluminal pressure due to mucin retention, which may lead to mucosal disruption or vascular permeation, allowing mucin to infiltrate the wall. However, this hypothesis remains speculative and requires further investigation. In LAMN cases with submucosal or deeper involvement, the extent of resection may warrant careful consideration, as discontinuous mucin infiltration may occur. These findings are hypothesis-generating, and further studies are needed to clarify the optimal surgical strategy.