Firstly, the liver often undergoes cirrhosis – from which a spectrum of well-differentiated hepatocellular nodular lesions of variable biologic status can evolve, namely, large regenerative nodule, low- and high-grade dysplastic nodules, and HCC. Secondly, the organ is a common depository for metastases – some nonhepatobiliary neoplasms can originate in the liver whilst others can mimic the two most

important primary liver cancers, namely, HCC and intrahepatic cholangiocarcinoma (ICC) (20,21). The diagnostic issues encountered in the morphologic workup of liver mass lesions are as follows: To separate well-differentiated hepatocellular nodular lesions from reactive hepatocytes To differentiate between the various view more benign well-differentiated Inhibitors,research,lifescience,medical Inhibitors,research,lifescience,medical hepatocellular nodular lesions, namely, large regenerative nodule, low- and high-grade dysplastic nodules, focal nodule hyperplasia and hepatocellular Paclitaxel human endothelial cells adenoma (+/- fatty change) To distinguish early HCC from benign well-differentiated hepatocellular nodular lesions To identify the variants of HCC and distinguish them from benign/malignant

mimics To differentiate intrahepatic cholangiocarcinoma (ICC) from metastatic adenocarcinomas To differentiate poorly differentiated HCC from poorly differentiated ICC To separate poorly differentiated Inhibitors,research,lifescience,medical primary liver carcinomas from metastases To recognize mixed hepatobiliary carcinomas and their permutations To establish histogenesis of benign/malignant nonhepatocellular tumors To determine primary site of origin of malignant nonhepatocellular tumors To distinguish benign from malignant cystic Inhibitors,research,lifescience,medical lesions To recognize inflammatory/infective lesions that may mimic tumors Although the title states the cytopathologic diagnosis of liver mass lesions, the authors have focused their review on primary and metastatic malignancies occurring in the liver. This is in essence a brief overview of their literature search for articles pertaining to the key cytologic characteristics of malignant liver lesions, Inhibitors,research,lifescience,medical diagnostic utility of immunohistochemical markers, and pertinent molecular tests. They mention important

AV-951 differential diagnoses and highlight common diagnostic pitfalls. Tumors with suspected metastatic disease can be divided into three main groups: (I) Tumors in which likely tumor and primary cite can be predicted with high level of confidence based on cytologic appearances, such as colonic adenocarcinoma, breast carcinoma, small cell carcinoma of lung and renal cell carcinoma; (II) Tumors having characteristic cytologic pattern but without specific clues to primary site, such as adenocarcinomas, squamous cell carcinomas, neuroendocrine tumors, lymphomas and melanoma; and (III) Undifferentiated neoplasms. Most of our comments pertain to practice in established centers with state-of-the art facilities and dedicated trained personnel to handle such focal liver masses from start to finish.