Unclassified hepatocellular adenoma expressing ASS1 associated with inflammatory hepatocellular adenomas.

Three liver nodules were fortuitously discovered in a 30-year-old obese woman during a gynecological workup and resected. Two nodules (6 and 1.5 cm) with histological characteristics of inflammatory hepatocellular adenoma (HCA) were C reactive protein positive with normal expression of glutamine synthetase. The third 6 cm nodule had all the characteristics of an Unclassified HCA with an overexpression of Argininosuccinate Synthase 1 (ASS1) in the tumor compared to the non-tumoral liver. The non-tumoral liver was highly steatotic. Upon MRI review, two HCAs were identified as inflammatory HCAs based on specific criteria. The third HCA was different from the other two with the presence of peculiar intratumoral fluid cavities. This first report on the association between unclassified HCA expressing ASS1 and inflammatory HCA reinforces the concept that common factors are implicated in HCA subtypes genesis. ASS1 is an interesting immuno-marker to identify among unclassified HCA a subgroup with a high risk of bleeding. ASS1 overexpression decreases sharply the number of "true" unclassified HCA.