Laparoscopic Right Hemicolectomy for Appendiceal Mucocele

Appendiceal mucocele is a rare disease with an incidence of 0.07–0.63% of all appendectomies and was first described in 1842 by Carl von Rokitansky. It is defined as an abnormal intraluminal accumulation of mucin. The clinical picture of AM can vary from asymptomatic mass in the right lower quadrant to symptoms of acute appendicitis. In some cases, AM can be found accidentally on CT performed due to other reasons or during surgery. Diagnosis consists mainly of imaging methods such as ultrasound, CT, and MRI with the finding of encapsulated cystic mass with calcifications. The main goal of surgical treatment is to remove an intact mucocele and prevent spillage of mucin into the peritoneal cavity. We present a case of large mucocele treated with laparoscopic right hemicolectomy.


INTRODUCTION
Appendiceal mucocele is a rare disease with an incidence of 0.07-0.63% of all appendectomies (1) and was first described in 1842 by Carl von Rokitansky (2). It is defined as an abnormal intraluminal accumulation of mucin (3). A mucocele is a result of the malignant transformation of goblet cells inside the lumen of the appendix (2). Previously, appendiceal mucocele (AM) was classified into four categories (simple/retention cyst, mucosal hyperplasia, mucinous cystadenoma, and mucinous cystadenocarcinoma) (4). A consensus for classification was reached in 2016 and it is suggested that AM should be used only as a clinical term, whereas diagnosis is based on histology (1).
The clinical picture of AM can vary from asymptomatic mass in the right lower quadrant to symptoms of acute appendicitis. Patients may also present with invagination, torsion, bleeding or AM can be misdiagnosed as an adnexal mass (5) or rarely as a chronic tubo-ovarian abscess (6). In some cases, AM can be found accidentally on CT performed due to other reasons or during surgery (5). Herein, we present a case report of appendiceal mucocele in a postmenopausal female patient.

CASE PRESENTATION
A 58-year-old female patient with a positive faecal occult blood test underwent colonoscopy with a finding of round shaped lesion with a diameter of 3 cm protruding into the caecal lumen. The mucosa of the caecum was without any pathological signs, although a compression was presented on the caecal wall due to an extraluminally localised lesion. Subsequently, a CT scan was performed, which showed a pathological fluid collection localised in the right lower quadrant. The lesion had features of a chronic abscess with calcifications in the wall. Other visceral organs were without any specific findings. The patient underwent magnetic resonance which revealed a cystic lesion in close contact with the caecal wall with the greatest diameter of 9 cm with internal septae.
In this patient, a laparoscopic revision was indicated and during the procedure, a whitish elastic well-bordered tumour with the size of 9.5 × 4 × 4 cm arising from appendix basis was found. There were no metastasis or ascites present in the peritoneal cavity. The tumour was fixed to the right colon, to the right lateral abdominal wall and re-troperitoneum. The right hemicolectomy was performed due to the tumor fixation to the adjacent structures to avoid mucocele perforation. The surgery was performed by a laparoscopic approach using the no-touch technique with the ileo-transverso-anastomosis. The specimen was removed within the endo-bag through mini-laparotomy.   Histological examination confirmed low-grade mucinous neoplasm of the appendix (LAMN). The specimen was delivered to the pathology department en-block without perforation. The appendix was dilated and filled with gelatinoid material. The cystic tumour of the appendix was lined with flat and a few isolated cylindrical mucinous epithelia with focal low-grade dysplasia. The growth of the lesion had an expanding pattern with the loss of muscularis mucosae and fibrosis of submucous tissue and muscular layer without any signs of perforation or propagation of the tumour cells into the serous layer. Six lymph nodes were identified only with features of chronic antigen stimulation. Resection margins were without any neoplastic changes. Adjuvant chemotherapy was not indicated, and the patient was followed up during the first year after the surgery every 3 months and during the second year every 6 months and underwent regular imaging and laboratory examinations. The last follow up was in January 2021 with no signs of recurrence. (6) or it can be found accidentally on imaging studies. Our patient did not have any specific symptoms except the positive faecal occult blood test.
Mucinous neoplasm represents a broad spectrum of tumours ranging from adenoma to mucinous adenocarcinoma. According to the recent classification from 2016, non-carcinoid epithelial tumours of the appendix are categorized into eight histomorphological groups which are summarized in Table 1  Appendiceal mucocele in some cases represents a diagnostic challenge. Abdominal ultrasound may reveal encapsulated cystic mass with or without acoustic shadowing caused by mural calcification. A pathognomonic for AM is the "onion skin sign" which refers to echogenic layers of mucin and acoustic shadowing caused by mural calcifications inside the lumen of a mucocele (2, 10). Furthermore, an appendix diameter of more than 1.5 cm and a wall thickness of more than 6 mm are considered to be the threshold values for AM diagnosis (10). Dilated low-attenuated encapsulated cystic lesion of the appendix is seen on CT. Intraluminal mucin accumulation causes chronic inflammatory changes which result in wall calcification which are characteristic for AM (2). In case of secondary intra-abdominal infection, there are signs such as peri-appendiceal fat stranding, free intraperitoneal fluid, calcification, and intraluminal air-fluid level shown on CT. Features such as wall irregularity and soft-tissue thickening highly support the malignant etiol-

DISCUSSION
Appendiceal mucocele represents an abnormal dilatation of the appendix with intraluminal mucin accumulation with an incidence of less than 1% (5). Mucocele is often diagnosed in patients over 50 years of age (4), whereas women are more often affected by this disease (7). Symptoms of AM are usually non-specific. Patients may complain of acute or chronic pain in the right lower abdominal quadrant and in some cases, a palpable mass can be present. Other common symptoms include also weight loss and changes in bowel habits (8). Some patients are admitted to the hospital due to symptoms of acute appendicitis and the diagnosis of AM is either established during surgery ogy of AM. Magnetic resonance shows AM also as a cystic mass with various T1W1 intensity and hyperintense on T2W1 (10). Furthermore, mucocele of the appendix can be associated with synchronous colorectal neoplasms in 19-25% of cases (11). Therefore a colonoscopy should be performed before surgery to assess the extent of surgical resection (10,12). A characteristic feature for AM can be found on colonoscopy known as "volcano sign" which is caused by fluctuation of protruded appendiceal ostium according to the respiratory movements (10). Tumour markers including CEA, CA 19-9 and CA-125 can be used in postoperative follow-up and their elevated levels may indicate recurrence (13), however, their diagnostic significance is low (2).
The goal of surgical treatment is to remove an intact mucocele, prevent spillage of mucin into the peritoneal cavity, and achieve negative resections margins (1). In case of spontaneous or iatrogenic perforation of AM, there is a high risk of pseudomyxoma peritonei development which is a severe complication with less than 20% of 5-years survival (14). Pseudomyxoma peritonei is a clinical syndrome characterized by the presence of mucin and neoplastic epithelial cells on the parietal and visceral peritoneum. This disease is a consequence of intraperitoneal dissemination from mucin-producing tumours (7). The treatment of PMP consists of cytoreductive surgery followed by hyperthermic intraperitoneal chemotherapy (15).
There are still no clear guidelines for surgical treatment of mucocele, however, Dhage-Ivatury et al. (16) and Kim et al. (17) created a scheme for the selection of the type of surgery. Several factors, which should be considered before the surgery, are summarized in table 1 (5). Frozen section examination of resection margins and sentinel lymph node (SLN) from mesoappendix is often useful and necessary to assess the extent of surgery. Right hemicolectomy is not indicated if SLN is without metastasis (18). Historically, laparotomy has been considered as the preferred surgical approach for mucocele treatment (4), however, there are several reports in the literature of successful laparoscopic mucocele resections. General principles of AM removal are the same regardless of the surgical approach. The operation should be performed carefully with an emphasis on the no-touch technique. An endo-bag must be used to prevent rupture of AM and port-site metastasis, while the surgeon should be experienced enough with laparoscopy (19). The prognosis of AM depends on several factors such as symptoms, histological parameters, perforation, increased tumour markers levels, and positive resection margins (20).

CONCLUSION
Appendiceal mucocele is a rare disease that can be asymptomatic or resembles acute appendicitis. Pre-operative diagnosis consists of imaging methods such as ultrasound, CT, MRI, or colonoscopy is used. The main goal of surgical treatment is to remove an intact mucocele and prevent spillage of mucin into the peritoneal cavity.