Benign nodules in post-Fontan livers can show imaging features considered diagnostic for hepatocellular carcinoma.

Purpose: To describe the imaging appearance of hyperenhancing nodules arising in post-Fontan patients and to identify specific features best correlated with malignancy.
Methods: Hyperenhancing hepatic nodules visible on CT and/or MRI in post-Fontan patients were identified retrospectively and reviewed by subspecialty radiologists. Nodules with characteristic imaging findings of focal nodular hyperplasia (FNH) were defined as typical, the remainder were defined as atypical, described in detail according to LIRADS criteria, and length of stability over time was recorded. Clinical data, alpha fetoprotein levels (AFP), central venous pressures (CVP), and histopathology were recorded.
Results: 245 hyperenhancing nodules (215 typical, 30 atypical) were evaluated in 30 patients. Twenty-nine atypical nodules showed washout (portal phase in 6, delayed phase in 29), 0 showed pseudocapsule, 1 showed threshold growth, 1 showed tumor in vein, and 5 showed ancillary features favoring malignancy. Pathology confirmed hepatocellular carcinoma (HCC) in 3 atypical nodules and FNH-like histology in 3 atypical and 4 typical nodules. 2 atypical nodules were present in a patient with clinical diagnosis of HCC. 20 nodules (7 typical, 13 atypical due to washout) were studied with hepatobiliary contrast agent and all showed homogenous hepatobiliary phase retention. Atypical nodules were significantly more likely to be HCC than biopsy-proven FNH-like or stable ≥24 months when showing portal phase washout (P < 0.001), mosaic architecture (P = 0.020) or in the presence of cirrhosis (P = 0.004) or elevated AFP (P = 0.004). Atypical nodules that were HCC had higher median CVP than those that were FNH-like (19, range 16-27 vs. 13, range 12-16 mmHg, P = 0.0003), there was not a significant difference based on median patient age (HCC 30, range 10-41 vs. FNH-like 40 range 10-41, P = 0.244).
Conclusions: Benign hyperenhancing masses in Fontan patients may demonstrate washout and be mistaken for HCC by imaging criteria. Portal phase washout, mosaic architecture, elevated AFP and higher CVP were associated with HCC in the atypical nodules found in this population.