Differential Diagnosis of Immunoglobulin G4-associated Cholangitis From Cholangiocarcinoma

BACKGROUND AND AIM Immunoglobulin G4-associated cholangitis (IAC) shares many similar symptoms with cholangiocarcinoma (CCA). However, the treatment and the prognosis are substantially different. This study aimed to identify the important markers for the differential diagnosis of these 2 diseases. METHODS Thirty IAC patients and 275 CCA patients were reviewed retrospectively for their clinical symptoms, serological tests, and imaging characteristics. Posttreatment responses were also studied. RESULTS IgG4 had 100% specificity for IAC at a cutoff of 6 times the upper normal limit. IAC patients had a significantly higher incidence of weight loss (P=0.025) and a higher level of weight loss (P=0.008) than CCA patients. The positive rates of biological markers CA199, CA242, and CEA in CCA and IAC were 81.5% versus 42.9%, 45.5% versus 4.5%, and 29.2% versus 7.1%, respectively. Levels of these tumor markers in CCA were significantly higher than in IAC (P<0.05). The thickened wall [17/18 (94.4%) vs. 3/10 (30%), P=0.001] and the occupying lesion on the bile duct [1/18 (5.6%) vs. 8/10 (80%), P<0.001] were found to be significantly different in IAC and CCA, respectively, by endoscopic ultrasonography. Autoimmune pancreatitis was the most frequently observed comorbidity of IAC (25/30). All IAC patients respond positively to steroid treatment. CONCLUSIONS Increased tumor markers, 6-fold higher levels of serum IgG4, and other organs' involvement could be the reference factors for a differential diagnosis of IAC and CCA. Endoscopic ultrasonography might be an effective imaging tool for diagnosis, although clinical signs and symptoms of IAC and CCA are similar. Experimental steroid treatment can be useful in the diagnosis for certain difficult cases.