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large, recent or old, macroscopically visible were present in 13 cases, only microscopic
in another one, absent in 1 case. In 13 cases, the tumors (T) had the same aspect: non
encapsulated, well differentiated proliferation, composed of clear often hypereosinophilic
packed hepatocytes, well vascularized by numerous arteries and veins, without noticeable
inflammation, ductular reaction, or steatosis. In 2 cases there were criteria of malignant
transformation: one classified as borderline HCA and another one with several HCC
foci. ASS1 was overexpressed in T compared to NT. In T, staining was diffusely or
heterogeneously distributed with a various intensity, whereas in NT, ASS1 was expressed
only in periportal and septal zones. In all other HCA subtypes and FNH, ASS1 expression
was downregulated (from absent to small patchy areas) compared to NT.

Conclusions: ASS1 immunostaining allows the classification of UHCA previously
defined by default (7 % of HCA), an HCA subgroup observed in women and with a
high risk of hemorrhage. ASS1 staining needs to be evaluated on liver biopsy to test its
relevance for patient management.

Disclosure of Interest: None Declared

ePOSTER ABSTRACTS

252 Programme & Abstracts • HCC Summit