The majority of appendix tumors are identified during laparotomies performed for acute appendicitis or other reasons. These tumors are rarely diagnosed preoperatively, even with advanced imaging techniques (1). Appendiceal mucoceles are masses caused by the dilation of the appendix lumen due to abnormal mucinous secretions.
Contents
Abnormal mucin accumulation may be due to retention, mucosal hyperplasia, cystadenoma, or cystadenocarcinoma. They are usually seen in individuals over 50 years of age and are more commonly observed in women (1,2). Although rare, this clinical entity has been reported in 0.2-0.3% of appendectomy specimens (2). This study presents a case of a mucinous cystadenoma diagnosed in a patient who underwent elective appendectomy for plastron appendicitis.
Case Report
A 32-year-old male patient presented to our emergency surgical clinic with complaints of abdominal pain persisting for three days. Upon clinical history, it was learned that the patient had experienced similar pain episodes in the past, but this time the pain was more severe. Physical examination revealed tenderness in the right lower quadrant, and a mass was palpable on deep palpation. No rebound tenderness was present. Laboratory tests showed a white blood cell count of 11,200/uL (normal range: 3800–10,000) and a CRP level of 99 mg/L (normal range: 0–5).
Abdominal ultrasonography (USG) revealed inflamed intestinal loops and mesenteric fat planes in the right lower quadrant consistent with plastron appendicitis, along with mesenteric lymphadenopathy. Since acute abdomen was not suspected, the patient was admitted for observation and medical treatment. The patient was started on cefazolin sodium 1g twice daily and ornidazole 500 mg twice daily. Three days later, the white blood cell count dropped to 9100/uL, and a follow-up USG showed a heterogeneous soft tissue mass, approximately 7 cm in size, consistent with plastron appendicitis and associated with the cecum.
The patient, who showed no complications by the seventh day of hospitalization, was discharged with the plan for elective appendectomy after three months. During the elective appendectomy, the middle third of the appendix appeared more swollen, while the root was normal and not adherent to surrounding tissues.
Standard appendectomy procedures were followed. While tumor-like lesions were suspected upon examination of the specimen, there was no observed invasion of surrounding tissues, and the surgery was completed. The patient, who experienced no postoperative complications, was discharged on the second postoperative day.
Pathological examination revealed that the appendix was 5.5 cm in length and 2.5 cm in diameter at its widest point, with mucinous material observed in the lumen. Microscopic examination showed increased nuclear stratification and mild pleomorphism in some areas of surface and crypt epithelium (Figure 1a). In one area, mucin extravasation into the surrounding adipose tissue of the appendix, accompanied by neutrophil infiltration, was observed (Figure 1b). Immunohistochemical staining with cytokeratin confirmed the absence of epithelial cells in the extravasated mucin. Based on these findings, a diagnosis of mucinous cystadenoma was made. During the patient's 32-month follow-up, no abnormalities were detected on CT scans or colonoscopy.
Discussion
The pathological condition of appendix mucocele was first described by Rokitansky in 1842, and the term was coined by Feren in 1876 (3).
A mucocele is the dilation of the appendix lumen caused by mucinous secretion. It is classified into four subgroups based on epithelial characteristics:
- Simple/retention mucoceles with normal epithelium and mild lumen dilation, often resulting from obstruction by fecal material.
- Mucoceles with hyperplastic epithelium, where lumen dilation is minimal, accounting for 5–25% of cases.
- Mucinous adenoma/cystadenoma, the most common form, representing 63–84% of cases. These often show villous adenomatous epithelial changes with mild atypia. The lumen can dilate up to 6 cm. Our case falls into this category.
- Malignant mucinous cystadenocarcinomas, accounting for 11–20% of cases. These are distinguished from other groups by glandular stromal invasion and/or epithelial cells in peritoneal implants. Lumen dilation is typically severe (4).
The last two groups are true mucinous neoplasms and may coexist with other neoplasms of the colon and rectum; thus, these patients should be evaluated for such associations (5). In our case, no abnormalities were found during a colonoscopy performed three months postoperatively.
Half of the patients are asymptomatic, and when symptoms are present, the most common is acute or chronic right lower quadrant pain. As in our case, long-standing vague discomfort or intermittent pain due to invagination of the dilated, mucus-filled appendix into the cecum can occur, along with a palpable mass (6).
Appendectomy remains curative even if complications such as focal mucin extravasation are observed. However, a ruptured cyst during surgery may lead to pseudomyxoma peritonei, necessitating careful handling to prevent spillage. Patients presenting with preoperative signs of mucocele should undergo appropriate imaging and surgical planning to minimize complications.
In conclusion, mucinous cystadenoma of the appendix is rare and can mimic plastron appendicitis. Diagnosis can be made preoperatively with USG or CT imaging or through histopathological examination of the resected tissue. Neoplastic lesions of the appendix should be considered in all cases presenting with a mass on imaging.
