Authors A. HOORENS (1), A. CANDAELE (1), M. VAN DER LINDEN (1), P. SMEETS (2), C. LECLUYSE (2), N. DE VOS (2), R. TROISI (3), J. VAN DORPE (1) / [1] Ghent University Hospital, Ghent, Belgium, Pathology, [2] Ghent University Hospital, Ghent, Belgium, Radiology, [3] Ghent University Hospital, Ghent, Belgium, General and Hepatobiliary Surgery, Liver Transplantation Service Introduction A 53-year-old woman was referred to our hospital because of a large liver mass. Her past medical history included an appendectomy as well as a hysterectomy with bilateral adnexectomy. There was no history of malignancy. She was treated with thyroxine. Aim The large liver mass was and incidental finding on computed tomography imaging after trauma. It was located in the left liver lobe and had a maximal diameter of 20 cm. In addition, a smaller lesion was observed in liver segment VI. On magnetic resonance imaging, the large lesion in the left liver lobe resembled a giant cavernous haemangioma, while the small lesion in the right liver lobe was suggestive of a hepatic adenoma. Methods Physical examination revealed the liver mass in the right hypochondrium, extending to below the umbilicus. It was slightly painful on palpation. Hand-assisted laparoscopic liver resection was performed of the left liver lobe in combination with resection of the lesion in segment VI. Results Macroscopically the left lobectomy specimen measured 20x16x8cm. A whitish red large liver mass was observed through the liver capsule. On cutting it had a varied appearance with cystic mucoid areas alternating with small fibrotic areas and haemorrhagic areas. The mass occupied almost whole the resection specimen and was sharply delineated from the surrounding liver parenchyma. The resection of segment VI measured 8x3x2cm. It contained an irregularly delineated mass with a maximal diameter of 2 cm. Microscopically, the tumour in the left liver lobe consisted of strands and nests of polygonal hepatocytes embedded in an abundant myxoid/mucinous matrix. The smaller lesion consisted of normal appearing hepatocytes arranged in cords, with focal peliosis and small foci of hepatocytes embedded in myxoid/mucinous stroma. None of the lesions contained portal tracts. Histology and immunohistochemistry was compatible with hepatocellar adenomas. The largest lesion was compatible with a myxoid hepatocellular adenoma. The smaller lesion was a more conventional type of hepatocellular adenoma, however, displaying some small foci of myxoid change, next to more prominent foci of sinusoidal dilatation and peliosis. Both tumours displayed inactivation of HNF-1-alpha expression, as demonstrated by loss of LFABP expression by immunohistochemistry. None of the tumours showed nuclear staining for beta-catenin, but the largest lesion expressed diffuse increased glutamine synthetase expression compared to non-tumoral liver parenchyma. Overexpression of glutamine synthetase was not observed in the smaller lesion. Conclusions Only very few cases of myxoid hepatocellular adenomas have been reported in the literature until now. Almost all described cases were associated with adenomatosis, and the myxoid change was present in multiple adenomas. Myxoid hepatocellular adenomas seem to be biologically distinct from other HNF-1-alpha mutated adenomas, as in addition to their typical morphology, malignant degeneration seems to more common. Reporting incidental cases is important to better understand the natural history of myxoid adenomas. Molecular characterization of these lesions may contribute to better predict the risk for malignant degeneration.
