Cytologic features and histologic correlations of microacinar and microtrabecular types of well-differentiated hepatocellular carcinoma in fine-needle aspiration biopsy

Abstract

BACKGROUND: Well-differentiated hepatocellular carcinoma (HCC) in fine-needle aspiration (FNA) biopsy is characterized by trabeculae three or more cells thick wrapped by peripheral endothelium. The authors encountered another pattern that did not fulfill these classic criteria for malignancy yet was proven to be HCC in clinical follow-up. The objective of this study was to characterize the cytologic features of this pattern with histologic correlations. METHODS: Over a period of 6.5 years, 14 of 123 cases (11.4%) of HCC from 428 liver aspirates showed the unusual pattern. Their cytologic features were compared with 14 cases of nonneoplastic liver on FNA smears that were processed with Ultrafast Papanicolaou stain, and their histologic features were compared on cell blocks with hematoxylin and eosin stain and reticulin stain. RESULTS: The unusual type of well differentiated HCC in FNA smears was characterized by numerous, small hepatocytes with minimal nuclear atypia but reduced cytoplasm, grouped together in microacini of five or more cells and microtrabeculae one or more cells thick of irregular thickness with no apparent peripheral endothelium. Transgressing capillaries were found when the smears were inspected carefully. In histology nine cases that were the compact type of HCC, two cases that were the microacinar type of HCC, and three cases that were the microtrabecular type of HCC. All FNAs showed deficient reticulin framework. All 14 cases of nonneoplastic liver aspirate were characterized by the presence of large tissue fragments that were resistant to smearing. CONCLUSIONS: Well differentiated HCC may present as microtrabeculae of irregular thickness one or more cells thick with inapparent peripheral endothelium or as microacini mimicking neuroendocrine carcinoma.