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Special Feature
December 21, 2009

Image of the Month—Diagnosis

Arch Surg. 2009;144(12):1185-1186. doi:10.1001/archsurg.2009.215-b
Answer: Mucinous Cystadenoma of the Appendix

Mucinous cystadenomas of the appendix are rare, accounting for between 0.2% and 0.3% of appendiceal specimens.1Approximately 25% are asymptomatic and discovered as an incidental finding.1They can present as vague right iliac fossa pain or rarely as bleeding or intussusception. Cystadenomas are notoriously difficult to diagnose preoperatively. Computed tomographic scans typically show a cystic mass arising from the cecum, dystrophic calcification of the wall, and intraluminal mucous.2Enhancing nodules in the wall are thought to indicate malignant cystadenocarcinoma,3although this has not been definitively proven, and the differentiation between benign and malignant lesions on radiological grounds remains difficult. The differential diagnosis includes duplication cyst, mesenteric cyst, and right ovarian cyst.

The pathological classification of mucocoeles into 4 groups (simple mucocoeles, mucosal hyperplasia, cystadenoma, and cystadenocarcinoma) based on the epithelial characteristics is a recent development. Its importance lies in the fact that management differs between groups. Simple mucoceles (also known as retention cysts) are lined with normal epithelium, with no dysplasia present. These can be treated by simple appendectomy. Focal or diffuse mucosal hyperplasia is the counterpart of the hyperplastic polyp in the colon. This is, in itself, a benign lesion, although it has been associated with large-bowel carcinomas and ovarian cystadenomas.4

A rare variant of appendiceal mucocoele, myxoglobulosis, has been described and accounts for between 0.35% and 8% of mucocoeles.5It is characterized by intraluminal globules containing mucous, giving rise to the term caviar appendix. Although morphologically dissimilar to the other appendiceal mucocoeles, these lesions may also be classified according to the epithelial characteristics. The majority are mucosal hyperplasias, although adenomatous changes have been described.5

Mucinous cystadenomas are lined by dysplastic epithelium, the equivalent of adenomatous polyps of the colon. Although no direct link with carcinoma has been proven, they coexist with colon cancer in up to 20% of cases.4Some series have reported pseudomyxoma peritonei associated with cystadenomas, although most authors currently believe this complication can only arise from malignant lesions.

Mucinous cystadenocarcinomas often cannot be distinguished from their benign counterparts on gross appearance; however, microscopically they demonstrate stromal invasion and/or the presence of epithelial cells in extra-appendiceal mucinous implants.4This latter characteristic is termed pseudomyxoma peritoneiand has a poor prognosis with a 5-year survival rate of only 25%.4

Because of the difficulty in distinguishing them from malignant cystadenocarcinomas, and the potential complication of rupture and subsequent pseudomyxoma peritonei, the recommended treatment for cystadenoma is full excision with oncological resection. If the lesion is confined to the body of the appendix, as in the case described herein, this can be achieved by appendicectomy including resection of the mesoappendix. For lesions that involve the cecum, or proven malignancy, the treatment of choice is right hemicolectomy. Because of the association with colorectal and ovarian malignancies, a follow-up colonoscopy and pelvic ultrasonography are warranted.

There is controversy about the use of laparoscopic appendicectomy to remove appendiceal mucocoeles, with some authors believing this to be a contraindication because of the risk of peritoneal seeding and subsequent pseudomyxoma peritonei. González Moreno et al6report a case where diffuse peritoneal carcinomatosis was discovered 9 months after laparoscopic resection of an appendiceal cystadenocarcinoma. A recent study by Rangarajan et al seems to contradict this, however, and quotes a series of 8 patients who all had successful laparoscopic resection, albeit for benign disease, and remained asymptomatic during 2-year follow-up.7

It seems laparoscopic resection is gaining popularity and is now seen as a feasible approach in the hands of experienced surgeons, provided suitable precautions are taken to avoid spillage and port site metastases.

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Article Information

Correspondence:Louise Clarke, MBChB, Department of Surgery, Redcliffe Hospital, Anzac Ave, Redcliffe, Queensland, Australia 4020 (louise_clarke@live.com).

Accepted for Publication:February 2, 2009.

Author Contributions:Study concept and design: Clarke and Lambrianides. Acquisition of data: Clarke and Lambrianides. Analysis and interpretation of data: Clarke, Lambrianides, and Lisle. Drafting of the manuscript: Clarke, Lambrianides, and Lisle. Critical revision of the manuscript for important intellectual content: Clarke and Lambrianides. Statistical analysis: Clarke. Administrative, technical, and material support: Clarke, Lambrianides, and Lisle. Study supervision: Lambrianides.

Financial Disclosure:None reported.

References
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Aho  AJHeinonen  RLauren  P Benign and malignant mucocele of the appendix: histological types and prognosis. Acta Chir Scand 1973;139 (4) 392- 400
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