HEPATOCELLULAR CARCINOMAS CYTOKERATIN 7-POSITIVE AND NEGATIVE: COMPARISON BY COMPUTERIZED MORPHOMETRY

Background and Aims: Although hepatocellular carcinoma (HCC) would be expected to express only CK8 and CK18, several Authors have described a subtype of HCC that express cytokeratins 7 and 19 (CyK7 and CyK19). The histogenesis of these HCCs has not been elucidated, but it has been supposed that these cells could be of progenitor cell origin that could be involved in HCC onset. Moreover, it has been suggested a worse prognosis for such HCCs. In this study, we have investigated by computerized morphometric the morphological features in HCC expressing CyK7 (CyK7-positive) and in HCCs CyK7-negative. Methods: This study included 10 HCC CyK7-positive from 10 patients submitted to LTx for HCV-related cirrhosis at the Niguarda Hospital in Milan. For each case, five consecutive sections 4 mm thick were obtained from the selected block. All specimens were stained with hematoxylin-eosin (H&E) and immunohistochemically for CD34 to assess the degree of sinusoidal capillarization, reticulin to assess the cell plate architecture and Ki67 to identify neoplastic cells that are actively dividing. We generated a computerized morphometric model to evaluate the volume fractions occupied by hepatocyte nuclei and cytoplasm, sinusoids, portal triads, capillarised sinusoids and tumor cells actively dividing. Lastly, the surface fraction occupied by reticulin was calculated. Moreover, tumor cells expressing both immunostains (CyK7/Ki67) were also identified. Results have been compared with a control group of 12 CyK7-negative HCC from 12 patients submitted to LTx. Results: On H&E stains, the features most discriminatory between HCCs CyK7-positive and CyK7-negative were volume fraction nuclei in unit volume and hepatocyte nuclear/cytoplasmic ratio. On immunohistochemistry, volume fractions of capillarised sinusoids and of Ki67 cells were prominent in HCCs CyK7-positive. In CyK7-positive HCCs, the expression of CyK7 correlated with the size of the lesion. Conclusion: Our morphometric model is an objective method of quantification of the morphologic features in both CyK7-positive and CyK7-negative HCCs and it could be applied in studies involving histological evaluation of the different subtypes of HCC arising in the cirrhotic liver according to their CyK7 expression.