Significance of endothelium in the fine-needle aspiration biopsy diagnosis of hepatocellular carcinoma

We reviewed fine‐needle aspiration biopsies (FNAB) of hepatocellular carcinoma (HCC) (n = 35), benign hepatic processes (n = 35), cholangiocarcinoma (CC) (n = 6), and metastatic tumors (n = 100) to evaluate the significance of endothelium present either peripherally‐wrapping around groups of cells, (peripheral endothelium (PE)), or transgressing sheets of cells (transgressing endothelium (TE)), in distinguishing these lesions. These patterns were assessed as absent, focal, or prominent. Thirty‐three of 35 (94%) HCCs contained either focal or prominent PE or TE, compared to only 3 of 35 (9%) benign hepatocytic lesions. Only one benign lesion contained a prominent endothelial component (TE only). Two cases of HCC failed to contain endothelium, one fibrolamellar variant and one well‐differentiated HCC. These differences were statistically significant (P < 10–5, sensitivity 94%, specificity 91%, and positive predictive value [PPV] 92%). Neither pattern of endothelium was present in any CC or metastatic tumor. These differences were also statistically significant (P < 10–5, sensitivity 94%, and specificity and PVP 100%). We conclude that the presence of endothelium, at least focally in either one or both distinctive patterns, is highly sensitive and specific for HCC and aides in distinguishing it from benign hepatocytic lesions, CC, and metastases. © Wiley‐Liss, Inc.