Cystic lesion of the gallbladder is uncommon and benign cystic lesion of the gallbladder is also very rare.1 Foregut cyst is a rare disease and foregut cysts below the diaphragm are usually found in the liver.2 Extrahepatic foregut cysts are very rare and can be found in the gallbladder, pancreas or upper gastrointestinal tract.3 To our knowledge, only 8 cases of foregut cyst in the gallbladder were reported.12456789 Herein, we presented a case of foregut cyst of the gallbladder and review of clinico-pathologic findings reported in the literature.

A 39-year-old female was referred to our hospital after abdominal ultrasonography revealed thickened wall of the gallbladder and a cystic lesion attached to the gallbladder. She had been admitted to a local hospital with right upper quadrant pain for 5 years. Tenderness of the right upper quadrant and Murphy's sign were present, but rebound tenderness was not present on physical examination. The results of laboratory examination indicated normal liver function tests, biliary enzymes and serum tumor markers. On abdominal ultrasonography and computed tomography, a unilocular cystic lesion was found at right upper quadrant with attachment to the gallbladder neck (Fig. 1A and 1B). Amorphous debris level was present in the cystic lesion. The gallbladder with cystic lesion was resected through laparoscopic cholecystectomy, in which there was no fibrosis or adhesion.

Grossly, the lesion revealed a unilocular cyst, measuring 3.5×3.2×3.0 cm, with mucin (Fig. 2). Microscopically, the cyst was lined with the ciliated cuboidal or columnar epithelium and abundant goblet cells (Fig. 3A). Squamous metaplasia or dysplasia was not present in the cystic epithelium. Dense smooth muscle layer or fibroelastic connective tissue was identified under the lining epithelium (Fig. 3B and 3C). Some eosinophils, lymphocytes and adipocytes were present in the fibroelastic connective tissue of the subepithelial layer (Fig. 3D). These findings led us to the diagnosis of ciliated foregut cyst and chronic cholecystitis. The postoperative course was unremarkable and clinical examination showed no evidence of recurrence in the 20 months following surgery.

Nam et al.8 first introduced the term 'ciliated foregut cyst of the gallbladder' in their case report of 2000. Ciliated foregut cysts are very rare benign cysts, arising from the remnant of the embryonic foregut and usually located above the diaphragm, which present either as a bronchial or esophageal cyst.58 When located below the diaphragm, they are usually found in the liver, where they are known as ciliated hepatic foregut cysts. More than 60 cases of the ciliated hepatic foregut cysts have been reported, but extrahepatic cysts are extremely rare.5 Only a few reports of the ciliated foregut cyst of the gallbladder were presented. Clinical manifestation and pathologic findings in literature and our case were summarized in Tables 1 and 2. Characteristically, all cases were middle-aged females and unilocular lesions. More than half of the cases were symptomatic, such as right upper or epigastric pain. Cystic lining cells usually consisted of pseudostratified columnar epithelium, and frequently single layer ciliated epithelium.1 A few or many goblet cells could be observed in the lining epithelium.248 Subepithelial layer consisted of fibroelastic tissue or thin smooth muscle layer similar to muscularis mucosa of gastrointestinal tract. Salivary gland acini could be found in the subepithelial area, similar to subepithelial glands of the bronchial wall.5 Some eosinophils, lymphocytes or adipocytes were observed in the fibroelastic tissue. Histopathologic feature of the gallbladder was unremarkable.

Clinically, unilocular cystic lesion is a suspected benign lesion rather than malignant lesion; and all reported ciliated foregut cysts of the gallbladder were unilocular. Even though ciliated foregut cyst of the gallbladder is benign, excision is needed to resolve patient's symptom and to rule out other benign or malignant cystic lesions including biliary cystadenoma, cystadenocarcinoma, cystic gastric heterotopias, cystic duct cyst and cystic lymphangioma.1011121314 Histologic examination and accurate pathologic diagnosis are essential to avoid unnecessary additional treatment, such as chemotherapy or radiotherapy for malignant neoplasm. However, the ciliated foregut cyst of the gallbladder mostly suggest benign cystic lesion on radiology.

Although lining epithelium of our case consisted of the ciliated cuboidal or columnar cells without squamous metaplasia, ciliated foregut cyst frequently shows squamous metaplasia.15 Squamous metaplasia is commonly observed in the uterine cervix or bronchial wall with chronic inflammation. Squamous metaplasia of epithelial cells can be induced in squamous cell carcinomas such as cervical squamous cell carcinoma of the uterus or squamous cell carcinoma of the bronchus.1617 There are a few reports of squamous cell carcinoma arising in the ciliated foregut cyst, however, there is no report on ciliated foregut cyst located in the gallbladder.181920 Ciliated foregut cyst requires surgical removal because of the frequent occurrence of squamous metaplasia and possibility of squamous cell carcinoma.