NET is derived from the embryonal neural crest cells called Argentaffin or Kulchitsky cells and have a potential for secreting serotonin. This tumor can arise anywhere in the distribution of the Argentaffin cell system. In addition to the most common sites of occurrence, namely, ileum and appendix these tumors have reported to occur in bladder, prostate, rectum, stomach, bronchi, pancreas, and biliary tree.

Primary Biliary Tract NETs are rare and account for 0.2%–2% [¹, ²] of all gastrointestinal neuroendocrine tumors.

The Literature documents about 77 cases of neuroendocrine tumor arising from the biliary tree which includes common bile duct, common hepatic duct, cystic duct, and hilar confluence.

We report a case of Primary Biliary NET arising from the left hepatic duct. An extensive search of the literature has yielded no reference regarding a NET arising from the left Hepatic ducts. The present case is the first reported case of a NET arising in the left hepatic duct.

A 69-years-old female presented with colicky pain in the right hypochondrium since 3 years. She had past history of open cholecystectomy done for gall stones 15 years back. On physical examination the patient was anicteric with soft abdomen. An Ultrasonography (USG) of the abdomen showed a hypoechoic lesion of size 3.5 cm × 4 cm in segment 4 of the liver. Computerized Tomography (CT) of the abdomen showed a 4.1 × 3.7 cm heterogeneously enhancing mass lesion in segment IV of liver abutting the left branch of portal vein (Figure 1). A Magnetic Resonance Imaging (MRI) of upper abdomen with Magnetic Resonance CholagioPancreaticography (MRCP) showed a filling defect in the left hepatic duct with lesion in the adjacent part of liver in segment IV, suggestive of a left hepatic duct tumor with infiltration in the liver (Figure 2). Tumor marker serum alfa fetoprotein was mildly raised. Patient was worked up for left hepatectomy. Intraopertaively a lesion arising from the left hepatic duct involving the left branch of portal vein and extending upto the portal confluence was found (Figure 3) rendering the tumor unresectable. A biopsy was taken from the mass and procedure was abandoned in view of inoperability. Histopathology showed typical rosette appearance of a neuroendocrine tumor (Figure 4) and immunohistochemistry positive for CD56, Chromogranin and Synaptophysin (Figure 5). Ultrastructural study of the cell with electron microscopy (Figure 6) showed the presence of multiple neurosecretory granules with muscle tissue.

A whole body Positron Emission Tomography (PET) scan and an Octreotride labeled radionulceotide scan showed somatostatin receptor expressing lesion in the hepatobiliary system (Figure 7).

The patient was started on long-acting Octreotride therapy single dose every month. The patient has received 12 of such doses and is doing well after a 1-year followup without any complications. A follow up MRI (Figure 8) upper abdomen with MRCP at 1 year showed the absence of filling defect in the Left hepatic duct that was seen previously which showed tumor regression.

Primary Biliary-tract NETs are very rare. They account for 0.2–2% of all gastrointestinal NET [¹, ²] reason being the paucity of enterochromaffin cells from which NETs arise in this area. Chronic inflammation of the bile duct epithelium is responsible for metaplasia of these enterochromaffin cells and formation of NET.

Davies [³] in 1959 reported NET of the distal bile duct and pancreatic duct which represented more of a periampullary NET rather than a biliary tract. Pilz [⁴] in 1961 was credited to report the first case of a Biliary Tract NET. After an extensive search of the Medline only 77 cases of Biliary Tract NET have been reported so far in the literature since 1961 (Table 1).

Till now no NET in the literature has been reported in the isolated left hepatic duct possibly making our case the first reported case of an isolated left hepatic duct NET.

The most common site of malignancy in the biliary tract was common bile duct (57.14%) followed by the hilar confluence (27.28%), the cystic duct (9.1%), common hepatic duct (5.12%) and finally the left hepatic duct (1.23%).

The mean age of presentation was 47 years (range 6 years to 79 years).

The male to female ratio is 1 : 1.23 showing that the biliary NET has a preponderance for female.

By far the most common symptom in patients of Biliary tract NET is Jaundice (63.4%) followed by Pain (14.1%), jaundice with pain (12.7%) and remaining nonspecific symptoms like weight loss.

The incidence of a Carcinoid syndrome in patients of Biliary Tract NET is very rare. Only 4 cases which include a single case published by Nesi et al. [⁵¹] in 2006 with symptoms of diarrhea due to secretion of serotonin and 3 cases by Price et al. [⁶⁵] in 2009 with features of Zollinger Ellison syndrome due to secretion of gastrin from tumor in CBD.

Biliary Tract NET are rare tumors that typically present with jaundice and pain. As compared to its counterpart Cholangiocarcinoma Biliary NET occurs in a younger age group with a female preponderance [³⁹]. Biliary NET usually are nonsecreting tumor. Preoperative diagnosis of these tumors require a high index of suspicion and accurate histopathological diagnosis which must include a immunohistochemistry study and electron microscopy. Biliary tract NET are slow-growing indolent tumor which have a limited propensity for local and metastatic spread. Surgical resection aimed at complete tumor excision with bilio-enteric continuity offers the best cure and high survival rates. Patients who have undergone resection have a long term survival. Even in inoperable patients chemotherapy with newer biologic agents like Octreotride have a favorable outcome on the patient's survival.

The authors declare that they have no conflict of interest.

We would like to thank Padmashree Dr. T. P. Lahane Dean of Grant Medical College Mumbai for the support and encouragement provided to publish this paper. We would also like to thank Dr. Sanjay Navani and Dr. M. B. Tayade Head of department General Surgery Grant Medical College Mumbai.