1.Primary sclerosing cholangitis (PSC)
PSC can be confused with bile duct cancer in its presentation. However, the issue of greatest concern is how to determine whether a patient with PSC has newly associated cholangiocarcinoma. Periductal infiltrative (PI-type) cholangiocarcinoma may produce jumping lesions that are very similar to the multiple strictures presented in PSC. In PI cholangiocarcinoma, the lesion is usually confined to one part of the biliary system, but in PSC patients, the lesion is usually diffusely distributed throughout the biliary system. The diagnostic role of PET-CT also needs to be further verified.
2.Cholangiocarcinoma embolism of liver cancer
Primary hepatocellular carcinoma with cholangiocarcinoma embolus, especially in patients with inconspicuous primary lesions, may have certain imaging similarities with cholangiocarcinoma of the hilar region, especially the intraluminal growth type, both of which can show bile duct obstruction in the hilar region and filling defects in the bile duct lumen. However, in fact, if it is noted that the patient has a past history of chronic hepatitis and cirrhosis, laboratory tests are mostly accompanied by elevated AFP and positive hepatitis virology, and CT/MRI shows splenomegaly and other manifestations of cirrhosis, the diagnosis is not difficult (see below).
3. Eosinophilic cholangitis and lymphoplasmacytic cholangitis
Eosinophilic cholangitis is a rare inflammatory solid occupancy that is usually thought to be due to an allergic cause because of the large number of eosinophils seen around the inflamed tissue. It is thought that eosinophilic cholangitis is a form of inflammation of the eosinophilic gastrointestinal (GI) tract that can affect other parts of the GI, including the stomach and pancreas. Stricture lesions can be long and multiple, and therefore similar to PSC. Patients with eosinophilic cholangitis respond well to systemic steroid administration. Steroid administration can be both a treatment option and a diagnostic test. Lymphoplasmacytic cholangitis has characteristics of an autoimmune disease that more commonly affects the pancreas. Some features of this disease are the same as those of PSC.
4. Benign inflammatory tumors
Benign inflammatory tumors, also known as inflammatory pseudotumors of the liver, benign fibrotic disease and pseudomalignant tumors at the porta hepatis. The masses consist of chronic inflammatory cells and fibrotic tissue. Benign inflammatory tumors are most commonly seen in the extrahepatic upper bile ducts, but also in the intrahepatic and least often in the lower bile ducts.
Benign inflammatory tumors are similar to malignant biliary obstruction in the porta hepatis and cause jaundice. The mean age at presentation of symptoms is 50 years, i.e., 10 years younger than the mean age at presentation of symptoms in patients with typical bile duct cancer. Inflammatory tumors cannot be distinguished from focal malignant strictures based on symptomatic presentation and liver function tests alone. Serum CA19-9 concentrations are usually normal or mildly elevated unless cholangitis occurs. However, approximately 20% of patients with malignant strictures also have normal serum CA19-9 concentrations. It is easier to identify cholangiocarcinoma if high concentrations of CA19-9 are detected or if vascular infiltration is present. In the absence of these two indicators, it is very difficult to differentiate benign inflammatory tumors from cholangiocarcinoma.
This benign inflammatory tumor accounts for 13-24% of all incidences of porta hepatis tumors. It is currently treated in the same way as cholangiocarcinoma – with surgical resection. If the diagnosis is not definitive, a direct intraoperative biopsy of the lesion may be performed, allowing the surgeon to confine the resection to the bile duct. Failure to clarify can lead to inappropriate treatment, such as long-term stent placement or hepatectomy.
5. Cholelithiasis and common bile duct stone disease
Common bile duct stones can be mistaken for bile duct cancer. When Mirizzi syndrome occurs, stones at the neck of the gallbladder in the inflamed gallbladder can compress the common bile duct, causing jaundice, fever and biliary colic are also more common. On radiological examination, the stricture of the common bile duct stones is usually located in the middle bile duct, which is smooth and narrow and curves to the left. Stones at the obstruction are usually adjacent to the stricture. They can be visualized by MRI or by combining direct cholangiography with ultrasound. The lesion may also be present as a separate right hepatic duct stenosis.
If the contrast can pass to one side of the stone, then the stone at the end of the lower bile duct is manifested on cholangiography as a bile duct stricture. This type of stone impaction can cause an inflammatory mass, increasing the suspicion of a tumor. The diagnosis can be confirmed if stones are detected by MRI, intraoperative ultrasound, or palpation. Multiple small stones in the bile duct may be confused with IG-type bile duct cancer. The differential diagnosis is based on the fact that tumors are enhanced on enhanced CT images, whereas stones tend to appear as smooth polyhedra on cholangiography.
6.Cholangiocarcinoma
Bile duct adenoma is a rare benign tumor, but can be easily confused with focal IG-type tumor (papillary bile duct carcinoma). In fact, adenomas may malign to papillary bile duct carcinoma, as do adenomas occurring in other parts of the body. These tumors characteristically present with jaundice or biliary colic, which may be polypoid and move with body position. filling defects in the bile ducts are seen on MRCP and CT images. If adenoma is suspected, the treatment option may be local biliary resection.
7.Cancer of gallbladder
The most common cause of malignant stenosis of the middle biliary tract of the common bile duct is not bile duct cancer, but is caused by compression or invasion of gallbladder cancer. Patients may present with painless or relatively painless jaundice, which is similar to cholangiocarcinoma. If gallstones are detected in the gallbladder, or if the wall of the gallbladder is thickened (sometimes in an off-center hypertrophy), especially in patients with enlarged gallbladder with mid-bile duct stenosis, it is highly suspected that gallbladder cancer has invaded the bile duct or bile duct cancer. Tumor invasion into the liver near the gallbladder bed may also increase the suspicion of gallbladder cancer rather than bile duct cancer. In the past, it was thought that once gallbladder cancer had invaded and obstructed the bile duct, its prognosis was often poor. However, our experience is that if there is a chance of radical treatment, its prognosis is better.
8.Neuroendocrine tumor of biliary tract
This is a rare slow growing tumor that may be jaundiced. Small masses may show arterial phase enhancement. Usually only local excision of the tumor and bile duct is required.
9. Granulocytic tumors
These tumors may arise from Schwann’s cells and occur very rarely in the biliary system. Tumors of the common bile duct or the confluence of the right and left hepatic ducts may cause biliary obstruction. Treatment includes surgical resection and the prognosis is good.
10. Bile duct sarcoma
This is a very rare tumor, usually embryonal rhabdomyosarcoma or smooth muscle sarcoma, which may present with jaundice and a mass may be found.
11.Lymph nodes
The lymph nodes in the hilar region of the liver may enlarge due to malignancy or inflammatory response. The enlarged lymph nodes may compress the bile ducts causing jaundice. Especially in gastric cancer, there is often lymph node metastasis to the hepatoduodenal ligament causing bile duct compression. Some of these patients may have significantly elevated AFP, which is generally not difficult to diagnose with routine gastroscopy.
12.Portal hypertensive bile duct lesions
These patients often have a long history of cirrhosis and portal hypertension. Jaundice and dilatation of intrahepatic bile ducts are not obvious and may have a long history with fluctuating clinical symptoms (sometimes heavy and sometimes light). There are no clear signs of bile duct obstruction on imaging. Usually tumor markers are not elevated. These patients must be handled with caution, and the situation will be very passive once they are operated as cholangiocarcinoma of the porta hepatis.