Low-Grade Appendiceal Mucinous Neoplasm Presenting as an Appendiceal Mucocele: A Case Report.

Appendiceal mucocele is an uncommon clinical and radiological finding characterized by cystic dilatation of the appendix due to intraluminal mucin accumulation and may be associated with underlying epithelial mucinous neoplasms. We present the case of a 45-year-old man with obesity who presented with a four-month history of intermittent right-lower-quadrant abdominal pain, occasional abdominal distension, and nonspecific changes in bowel habits. Physical examination revealed localized tenderness without signs of peritoneal irritation, and laboratory findings were within normal limits. Abdominal ultrasonography demonstrated a cystic tubular structure in the right iliac fossa. Contrast-enhanced computed tomography of the abdomen and pelvis showed a dilated appendix measuring approximately 22 mm in diameter, with homogeneous low-attenuation intraluminal content, wall thickening, and mural calcification, without radiological evidence of perforation, abscess, ascites, or invasion of adjacent structures. Based on these findings, an appendiceal mucocele without radiological signs of complication was suspected. Because the lesion was closely associated with the cecal region and limited appendectomy was considered unsafe due to the risk of rupture or incomplete gross resection, the patient underwent elective open right hemicolectomy with stapled ileotransverse anastomosis. Careful surgical handling was performed to avoid appendiceal rupture and mucin spillage. The postoperative course was uneventful. Histopathological examination confirmed a low-grade appendiceal mucinous neoplasm (LAMN) measuring 10 cm in length and 2.2 cm in diameter, with an uninvolved appendiceal base and no extra-appendiceal mucin, microscopic perforation, invasive adenocarcinoma, or high-grade malignant features. This case highlights the importance of multidisciplinary assessment and risk-adapted follow-up in patients with suspected appendiceal mucinous lesions.