How do I distinguish cholangiocarcinoma from metastatic carcinoma and why does it matter?

The 2019 WHO classification recognizes two morphologic variants of cholangiocarcinoma: 1) small duct type, and, 2) large duct type; the former is associated with IDH1/2 mutations and FGFR2 fusions. Therapies targeting these genetic alterations have recently been approved by the FDA. The liver is a favored site of metastasis in the body, and it is thus imperative to distinguish metastatic adenocarcinoma from cholangiocarcinoma. The traditional diagnostic approach employs immunohistochemical stains to exclude a metastatic carcinoma.
Source: Diagnostic Histopathology - Category: Pathology Authors: Tags: Mini-symposium: Tumours of the liver and biliary tree Source Type: research