Hepatic resection for inflammatory hepatocellular adenomas: pathological identification of micronodules expressing inflammatory proteins

Background Inflammatory hepatocellular adenoma (IHCA) defines a subgroup of hepatocellular adenomas characterized by the expression of members of the acute-phase inflammatory response [(serum amyloid A protein (SAA) and C-reactive protein (CRP)]. IHCA are unique or multiple as defined by the presence of several nodule(s) larger than 10 mm using both imaging and macroscopic observation. Frequently, additional micronodules (< 10 mm), previously undetected by imaging, can be observed in resected specimens. Aims To analyse micronodules in multiple (group 1, nine patients) and single (group 2, eight patients) IHCA cases, immunohistochemistry using SAA and CRP antibodies was performed on all nodules detected under macroscopic examination as well as on surrounding tissue with no visible nodules. Results Nodules of different sizes (> 5 < 10 mm, >= 1 < 5 mm) were found in group 1, whereas only rare nodules in the mm range were found in group 2. Micronodules shared the characteristics of large nodules, which justified surgery such as inflammatory infiltrates, abnormal arteries, sinusoidal dilatation or peliosis. However, the number of these characteristics was proportional to the size of the nodules. Conclusion This study demonstrates that the real number of IHCA is greater than that predicted from imaging-based analyses. In addition, we show that patients with more than one nodule present a greater chance to display more and larger undetected micronodules than patients with a single nodule.