Wen KW, Rabinovitch PS, Wang D, et al. - Since the differentiation between well-differentiated intrahepatic cholangiocarcinoma (iCCA) from its morphological mimics like bile duct adenoma (BDA) and hamartoma (BDH) may be difficult, especially in small biopsies researchers have examined the utility of DNA flow cytometry to distinguish between malignant and benign intrahepatic biliary lesions. They conducted DNA flow cytometry on 47 formalin-fixed paraffin-embedded samples of iCCA, 14 BDA, and 18 BDH. The frequency of aneuploidy was significantly higher in iCCA (47%) than in its benign morphological mimics (0%), indicating that it may potentially serve as a diagnostic marker of malignancy in difficult circumstances. The results also indicate that most BDAs and BDHs, if not all, are benign entities and do not represent iCCAs precursor lesions that frequently harbor aneuploidy. Although a larger cohort may be required to further establish the prognostic significance of aneuploidy in postresection iCCA patients, patients with aneuploid tumors may have a higher risk of tumor progression, particularly during the first 3 years.