Choi, Eun-Young Karen

Listing and transplanting patients with acute liver failure (ALF) is challenging, requiring rapid assessment of the likelihood of recovery. The availability of a large number of ALF liver explants, along with their clinical data, afforded an opportunity to retrospectively evaluate liver transplantation (LT) decision-making. We hypothesized that, with the benefit of hindsight, a small number of patients might have recovered without LT. Three hundred liver explants from ALF patients of varying etiologies who had undergone LT over 22 years in the Acute Liver Failure Study Group registry were reviewed for histopathological features and degree of necrosis by a committee of 8 hepatopathologists. A second committee of 8 experienced transplant hepatologists independently reviewed clinical data on these same 300 patients and retrospectively scored the likelihood that each patient required transplantation. Only 3 (1%) of those reviewed by the Clinical Committee were considered to “Definitely” not require liver grafting, while an additional 10 (3.3%) were deemed to “Possibly” not require transplantation (Not Likely Group, N=13). There was no difference in the degree of necrosis in explants in these groups, when compared to the remaining Likely Group, N=287 (95.6%), except in acetaminophen (APAP)-associated ALF, where the degree of necrosis was more uniformly graded as severe, correlating with the need for transplantation. Virtually every patient undergoing LT for ALF retrospectively appeared to need their transplant, based on expert clinical consensus review. Overall, there was poor correlation between clinical severity and apparent degree of necrosis seen in the 300 liver explants, except perhaps for APAP subjects.

Several reports describing a rare primary liver tumor with histologic features reminiscent of follicular thyroid neoplasms have been published under a variety of descriptive terms including thyroid-like, solid tubulocystic, and cholangioblastic cholangiocarcinoma. Although these tumors are considered to represent histologic variants, they lack classic features of cholangiocarcinoma and have unique characteristics, namely immunoreactivity for inhibin and NIPBL::NACC1 fusions. The purpose of this study is to present clinicopathologic and molecular data for a large series of these tumors to better understand their pathogenesis. We identified 11 hepatic tumors with these features. Immunohistochemical and NACC1 and NIPBL fluorescence in situ hybridization assays were performed on all cases. Four cases had available material for whole-genome sequencing (WGS) analysis. Most patients were adult women (mean age: 42 y) who presented with abdominal pain and large hepatic masses (mean size: 14 cm). Ten patients had no known liver disease. Of the patients with follow-up information, 3/9 (33%) pursued aggressive behavior. All tumors were composed of bland cuboidal cells with follicular and solid/trabecular growth patterns in various combinations, were immunoreactive for inhibin, showed albumin mRNA by in situ hybridization, and harbored the NIPBL::NACC1 fusion by fluorescence in situ hybridization. WGS corroborated the presence of the fusion in all 4 tested cases, high tumor mutational burden in 2 cases, and over 30 structural variants per case in 3 sequenced tumors. The cases lacked mutations typical of conventional intrahepatic cholangiocarcinoma. In this report, we describe the largest series of primary inhibin–positive hepatic neoplasms harboring a NIPBL::NACC1 fusion and the first WGS analysis of these tumors. We propose to name this neoplasm NIPBL:NACC1 fusion hepatic carcinoma.