Autoimmune cholangitis and cholangiocarcinoma.

Autoimmune cholangitis, immunoglobulin G4-associated cholangitis (IAC), is a part of multiorgan IgG4-related systemic disease, which was recognized as a new clinicopathological entity in recent years. IAC is defined as a biliary stricture that responds to steroid therapy, frequently is associated with other fibrosing conditions, especially autoimmune pancreatitis and is characterized by elevation of IgG4 in serum and infiltration of IgG4 positive plasma cells in bile ducts. Since IAC shares a number of clinical, biochemical, and imaging features with cholangiocarcinoma (CCA), it is often misdiagnosed as CCA, and unnecessary surgery was performed. In this compact review, we clarify the disease of IAC, summarize criteria for diagnosis of IAC, discuss the role of CA 19-9, and provide key information to differentiate diagnosis of IAC from CCA. IAC should be highly suspected in unexplained biliary stricture associated with increased IgG4 (in serum especially in bile) and other organ involvement (kidney, retroperitoneum etc. especially pancreas in which there are abundant IgG4-positive plasmocytes infiltration). Correct diagnosis of IAC will avoid unnecessary surgery because IAC responds well to steroid therapy. In a word, increased IgG4 levels, other organ involvement and response to steroids are keys to distinguishing IAC from CCA.