A case of appendiceal mucocele mimicking adnexal mass in a young woman with chronic abdominal pain

Low-grade appendiceal mucinous neoplasm (LAMN) is a very rare condition, diagnosed in 0.2-0.7% of appendectomies. The pathophysiology of the neoplasm involves accumulation of large volume of mucin in the appendiceal lumen, resulting in its obstructive dilation. Most epithelial tumors affecting the appendix are of the mucinous type and are manifested by mucin accumulation within an inflamed appendix with fibrotic and hyalinized wall.

A 29-year-old female presented with a history of chronic and intermittent episodes of abdominal pain and a palpable mass in the right lower abdominal quadrant. Sonography showed a 58 mm mass anterior to the uterus and adjacent to the ovary, probably a uterine myoma. Laparotomy revealed normal uterus, and ovaries with a translucent mass originating from the appendix and fixed to the cecum. Pathologic examination of the mass was reported as low grade appendiceal mucinous neoplasm.

This is a rare case of appendiceal mucocele in a young female, mimicking a pelvic mass, which was misinterpreted by sonography as a gynecologic solid mass near the uterus. Preoperative diagnosis of appendiceal mucocele is important due to the risk of concurrent GI and ovarian malignancy associated with the condition.