Low grade appendiceal mucinous neoplasm mimicking an ovarian cyst: A case report

Appendiceal mucocele (AM) is a very rare neoplasm with an incidence of 0.2-0.3% of all appendectomy specimens. AM usually defined as an intraluminal dilation of the appendix in response to mucin accumulation. The preoperative diagnosis is difficult and can be misdiagnosed to any of the other differential diagnosis especially in female patients. If it is suspected, imaging modalities and colonoscopy can be helpful as a guide for the right surgical approach.

A 41-year-old lady who found to have an appendicular tumor discovered incidentally on magnetic resonance imaging (MRI) of the abdomen during a follow-up in the referral hospital for persistent right lower quadrant abdominal pain with enlarging right ovarian cyst for 2 years. MRI revealed a sizeable cyst measuring 7 × 4 × 3 cm in the right iliac fossa (RIF) region with high suspicion of an AM. The patient was managed with open right limited hemicolectomy. The patient was diagnosed as a well-differentiated low-grade AM neoplasm with stage 0 (pTis, pN0, M0) based on the 8th edition of the American Joint Committee on Cancer (AJCC) Staging System. The patient had an uneventful recovery and advised for regular follow-up of at least 5 years.

AM is a very rare neoplasm. The imaging modalities that can be diagnostic methods are the abdominal ultrasonography (US), transvaginal US, abdominal computed tomography (CT) and abdominal MRI. Fine needle aspiration must be avoided as the risk of perforation is high that will lead to dissemination of the mucinous material causing a serious complication called pseudomyxoma peritonei. Laparotomy is superior on laparoscopy as the risk of perforation is lower in laparotomy.

The presentation of AM is usually not specific, because of its anatomic position. Physicians should consider it in the differential diagnosis of persistent enlarging ovarian cyst or adnexal mass.