Tumors of Appendix: Issues in the management of Mucocele of the appendix

Background
Mucocele of the appendix (0.2 – 0.3% of appendectomy specimens) is a morphologic descriptive term for obstructive dilatation of the appendix by intraluminal accumulation of mucoid material.^1,2 As such MA is not a pathologic diagnosis and can arise from various non neoplastic, benign neoplastic or malignant conditions. The clinical importance of MA arises from the fact that it is the primary cause of pseudomyxoma peritonei (PP). Curative surgery for MA mandates R0 resection without iatrogenic peritoneal spillage of mucinous material.³

The MA is often a postoperative diagnosis and most of the current literature therefore provides management options primarily based on histopathological diagnosis (such as adenoma or mucinous adenocarcinoma) following appendectomy. With this strategy many patients particularly those with malignant mucinous tumors need completion second surgery. Additionally there is risk of mucin spillage and chance of cure compromised.

In present times due to an increased awareness and easy access to abdominal contrast enhanced computed tomography (CECT), a diagnosis of MA prior to surgery is more likely. We share our experience in managing one such patient.

Brief case presentation

A 61 year old non smoker, gentleman presented with complaints of colicky pain abdomen of 20 days duration. Abdominal examination was unremarkable except for mild tenderness in right iliac fossa. On abdominal CECT, there was mural calcification in MA and no other abdominal malignancy was detected (Figure 1). 

Figure 1. CECT abdomen

Patient had an elevated CEA (6.3ng/ml). Further work up with colonoscopy did not reveal any synchronous colorectal malignancy.  In view of the elevated CEA levels and that with existing medical literature it is very difficult to differentiate benign from malignant mucocele of the appendix preoperatively he was advised laparoscopic ileo-cecal resection with extracorporeal ileo-ascending anastomosis (Figure 2). He had an uneventful postoperative period and was discharged from the hospital on postoperative period 7.

Figure 2. Surgery specimen - displaying mucocele of the appendix

The CEA levels returned to normal (<3 ng/ml) on 7^th postoperative day and was discharged from the hospital on POD7. The biopsy revealed benign cystadenoma and tumor mucosa stained positive for CEA on immunohistochemistry.

Issues in the management of preoperatively diagnosed - Localized mucocele appendix (MA)

1.      Are there any indicators for malignancy? What is the role of CECT and elevated carcinoma embryonic antigen (CEA)?

The current multidetector CECT scans have accuracy in excess of 85% for definitive diagnosis of MA.⁴ The differentiation of benign from malignant etiology however remains difficult. Imaging features such as soft tissue thickening (internal soft tissue attenuation nodularity) and irregular walls contour (as opposed to smooth) are reported to be significantly associated with malignant lesions.² The radiological features not predictive of malignancy include: dimensions of short diameter of mucocele, presence of calcification, maximal wall thickness and internal septations.² The experience with other modalities such as positron emission tomography is very limited. Abdominal CECT therefore may be regarded as the imaging modality of choice for diagnosis and treatment planning.

CEA levels may be elevated in patients with benign cystadenoma and high values are not necessarily indicative of malignancy. These may return to normal after surgical resection. Similar findings have been reported in few other reports also. ⁵

A thorough evaluation to rule out synchronous colorectal and other malignancies is indicated in all patients with MA irrespective of the CEA levels.^6,7

2.      What should be the extent of surgery?

All medically fit patients with MA should be planned for R0 resection without spillage of mucinous material (https://jamanetwork.com/journals/jamasurgery/article-abstract/2601315).³ At surgery a thorough evaluation of peritoneal cavity is performed to rule out any evidence of peritoneal dissemination. In those with localized MA, the extent of surgery is guided by findings on abdominal CECT – likely malignancy and anatomical extent of disease. The patients with likelihood of malignancy should be advised to undergo oncologic right hemicolectomy.^6,7

 For those with involvement of appendicular base, simple appendectomy in all likelihood would result in margin positive resection and mucin spillage. Hence appropriate surgery for such patients is ileocecal resection .³ Remaining patients with distal MA likely due to benign on abdominal CECT scan may undertake appendectomy (without mucin spillage) with excision of mesoappendix. In case of doubt pertaining to the anatomic extent of disease or malignancy, right hemicolectomy and not appendectomy should be the preferred option.

3.      Is MIS a safe option in presence of MA?

An 'open' surgical approach is preferred by many due to possibility of rupture of mucocele during laparoscopic manipulation. All patients in the present study underwent laparoscopic ileocecal resection with extracorporeal anastomosis (no tumor rupture). The guiding principle was 'no touch' technique whereby MA was not directly grasped by surgical instruments. Many recent publications have also demonstrated MIS to be a safe surgical option for MA.^8,9

The strength of our strategy is that it is likely to provide a potentially curative resection and avoid completion second surgery in vast majority of this subgroup of patients. We appreciate that no imaging modality is infallible and few patients deemed benign on abdominal CECT may have malignant disease on final histopathology. They are managed as per existing protocols for postoperatively diagnosed MA.

References:

1.      Dhage-Ivatury Shubhada, Sugarbaker Paul H. Update on the surgical approach to mucocele of the appendix. J Am Coll Surg. 2006;202(4):680-684.
https://www.journalacs.org/article/S1072-7515(05)01859-4/abstract

2.      Wang H, Chen YQ, Wei R, Wang QB, Song B, Wang CY, Zhang B. Appendiceal mucocele: a diagnostic dilemma in differentiating malignant from benign lesions with CT. AJR. 2013;201(4):W590-595.
https://www.ajronline.org/doi/full/10.2214/AJR.12.9260

3.      Vashistha N, Aggarwal B, Singhal D. Incidentaloma in the right iliac fossa. JAMA Surg. 2017;152(4):405-406.
https://jamanetwork.com/journals/jamasurgery/article-abstract/2601315

4.      Crichlow L, Jaffe BM, Bellows CF. Image of the month. Low-grade appendiceal mucinous neoplasm. Arch Surg 2012; 147(8):781-2.
https://jamanetwork.com/journals/jamasurgery/fullarticle/1351831

5.      McFarlane MEC, Plummer JM, Bonadie K. Mucinous cystadenoma of the appendix presenting with an elevated carcinoembryonic antigen (CEA): report of two cases and review of the literature. Int J Surg Case Rep. 2013;4(10):886-888.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3785880/

6.      Nitecki SS, Wolff BG, Schlinkert R, Sarr MG. The natural history of surgically treated primary adenocarcinoma of the appendix. Ann Surg. 1994;219:51-57.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1243090/

7.      Stocchi L, Wolff BG, Larson DR, Harrington JR.Surgical treatment of appendiceal mucocele. Arch Surg. 2003;138:585-590.
https://jamanetwork.com/journals/jamasurgery/fullarticle/394931

8.      Rangarajan M, Palanivelu C, Kavalakat AJ, Parthsarthi R. Laparoscopic appendicectomy for mucocele of the appendix. Indian J Gastroenterol. 2006;25:256-257.
https://www.ncbi.nlm.nih.gov/pubmed/17090846

9.      Park KJ, Choi HJ, Kim SH. Laparoscopic approach to mucocele of appendiceal mucinous cystadenoma: feasibility and short-term outcomes in 24 consecutive cases. Surg Endosc. 2015;29(11):3179-3183.
https://link.springer.com/article/10.1007%2Fs00464-014-4050-4

Authors:

Dr Nitin Vashistha, MS, FIAGES, FACS

Dr Dinesh Singhal, MS, FACS, DNB (Surg Gastro)

Department of Surgical Gastroenterology,
Max Super Speciality Hospital, Saket, New Delhi, India
E mail: gi.cancer.india@gmail.com

www.gicancerindia.com