Clinicopathological characteristics of sonic hedgehog hepatocellular adenomas with special focus on small lesions

Sonic hedgehog hepatocellular adenomas (sh-HCA) are prone to bleed. Focusing on small sh-HCA (1-4 cm), we documented and compared their clinicohistopathological characteristics, with those observed in large sh-HCA nodules (5-9.5 cm), including the cause of surgery and association with symptomatic bleeding.

Macroscopic and microscopic features of resected sh-HCA were reviewed in 17 patients divided in three groups: group 1a corresponding to seven patients with sh-HCA nodules of 5 cm and larger; group 1b: the same patients of group 1a whose resected specimens contain nodules smaller than 5 cm, and group 2: 10 patients with sh-HCA smaller than 5 cm, resected for variable indications. The diagnosis of sh-HCA was confirmed by immunohistological overexpression of arginosuccinate synthase-1 with molecular demonstration of activation of the sonic hedgehog pathway in 9/17 cases and robust exclusion of other HCA subtypes. Clinical data were available with focus on bleeding signs in all patients.

All 17 patients showed similar clinical characteristics. Macroscopic haemorrhage and microscopic features of vascular damage such as sinusoidal dilatation, congestion, ischaemic changes, microhaemorrhage and fluid-filled cavities were found in both larger and smaller nodules, independent of their sizes and mode of discovery.

Our results showed that small sh-HCA, whatever their mode of discovery, are histologically similar to the larger ones. These similarities in the vascular-circulatory histopathological features, regardless of the size of the adenomas, emphasized the bleeding tendency of sh-HCA. Necrotico-haemorrhagic areas may gradually reduce the size of the tumour, in which case a conservative approach may be considered.