A 33-year-old woman presented to the emergency department at our hospital with recurrent episodes of right-upper-quadrant pain associated with multiple episodes of vomiting. She had an ultrasonographic scan of the abdomen that showed multiple mobile stones in the gallbladder with normal intra- and extrahepatic bile ducts with no other abnormality. The blood workup was normal including liver function tests. She was operated for a laparoscopic cholecystectomy on an ambulatory surgery basis. The operation was uneventful except for the finding of a 1.5-cm nodule within the triangle of Calot (Fig. 1). This well-circumscribed, spherical lesion was attached to the common hepatic duct and embedded within the triangle of Calot with no communication to the hepatic parenchyma or gallbladder. Upon this abnormal finding, which we assumed to be an abnormally large cystic lymph node, an on-table cholangiogram (Fig. 2) was performed that showed normal biliary anatomy, no filling defects within the biliary tract and normal flow of the contrast material into the second part of the duodenum (Fig. 3). The node was bluntly and sharply dissected off the common hepatic duct, and it showed not to be related to the cystic artery and was separate from the cystic lymph node. No communication between the cystic structure and the common hepatic duct, the cystic duct or any vascular structures could be demonstrated, except for thick fibrous tissue attaching the mass to the distal part of the common hepatic duct. The operation was otherwise uneventful for any complications, and the patient was discharged on the same day. Histopathological examination showed the gallbladder to be chronically inflamed and the node to be 1.5 cm in greatest diameter. This node is a unilocular cyst (Fig. 4) lined with pseudostratified ciliated epithelium admixed with mucinous cells. Underlying this epithelial layer, connective tissue stroma, a thin layer of smooth muscle cells and an outer fibrous layer were identified. No communication or ductal structures could be found. Furthermore, immunohistochemical staining showed the cyst to be cytokeratin 7 (CK7) positive and cytokeratin 20 (CK20) and CDX2 negative. These histological findings are consistent with a ciliated foregut cyst. With this final diagnosis, the pre-operative ultrasonographic scans were reviewed retrospectively (Fig. 5). The possibility of the presence of a cystic structure separate from the gallbladder and the common hepatic duct was entertained. Obviously, such a subtle finding would have been easily missed pre-operatively taking into consideration the patient’s presentation, described above.
Discussion
Ciliated foregut cysts (CFC) are extremely rare, benign, congenital cystic lesions that arise from the embryonic primitive foregut [1]. These cysts are most often solitary and unilocular characterised by an internal pseudostratified, ciliated, mucin-secreting, columnar epithelial lining [1]. These lesions are usually located above the diaphragm [2, 3] with a few reports of ciliated cysts in relation to abdominal organs.
During embryonic development, the differentiation of the primitive foregut cells gives rise to the oropharynx, oesophagus, larynx, tracheobronchial tree, lungs, stomach, proximal duodenum, pancreas, liver and biliary system [3–5]. The presence of cysts with a respiratory-type epithelial lining in relation to abdominal organs is aberrant. However, it is postulated that the same mechanisms underlie the development of CFC in relation to abdominal organs and the respiratory system [3, 10].
Consequently, the association of CFC with the biliary system is quite exceptional. The first description of these lesions in the gallbladder was by Kakitsubata et al. in [6]. A ciliated cyst of the common bile duct was reported by Baranger et al. in [7]. In 2000, Nam et al. were the first to introduce the term ‘ciliated foregut cyst of the gallbladder’ in their report [5]. Five other reports described ciliated cysts found within the wall of the gallbladder [2–4, 8, 9].
The differential diagnosis of hepatic CFC would include biliary cyst, parasitic cyst, mucinous cystic neoplasm and various cystic metastases, such as cystic neuroendocrine tumour or necrotic metastases. When identified in the gallbladder fossa, a pancreatic pseudocyst, choledochal cyst or gallbladder duplication should also be considered [10].
To our knowledge, this is the first description of a ciliated foregut cyst in the triangle of Calot presenting as a unilocular cyst that is attached by fibrous tissue to the common hepatic duct and is totally extramural and without any communication to the gallbladder or the hepatic ducts [10].
This case highlights the diagnostic challenges and management options posed by this pathological rarity. In this case, the pre-operative ultrasound scan could not specifically identify the presence of the cyst, and an intra-operative cholangiogram could not prove a communication between the cyst and the biliary tracts. Furthermore, there were reports on the transformation of hepatic ciliated foregut cysts into primary squamous cell carcinoma [9, 10]. The exceptional presentation of such a lesion precludes firm conclusions in this regard. As malignant potential cannot be totally excluded and in the absence of well-defined surveillance criteria, the excision of these tumours, when diagnosed, would be a rational approach mainly in young and symptomatic patients.
