Focal Nodular Hyperplasia or Mass Effect?
Bronwyn H Bryant, Melissa P Upton, Paul E Swanson, Matthew M Yeh, Maria Westerhoff. University of Washington, Seattle, WA
Background: Focal nodular hyperplasias (FNH) are liver masses that often do not warrant surgical resection. However, it is possible that directed biopsies may miss true target lesions and biopsy adjacent liver with findings similar to FNH. Recently, glutamine synthetase (GS) has been demonstrated to express a distinctive map-like immunoreactivity in FNH. We tested GS in multiple types of non-FNH liver lesions, hypothesizing that the hepatic parenchyma around these lesions may demonstrate FNH-like staining patterns, with the potential pitfalls of a misleading diagnosis of FNH on biopsy and the risk of missing resectable target lesions.
Design: 19 metastatic neuroendocrine tumors (NE), 21 metastatic colon carcinomas (CC), 5 FNH, and 7 chemoembolized hepatocellular carcinomas (HCC) from 28 men and 24 women (age range 34-81, mean age 55.8) were evaluated based on H&E characteristics and GS immunostaining. Each lesion was assessed for size, degree of fibrosis present within the main mass (scored 1-3), the presence or absence of FNH-like features in the liver surrounding the mass, and pattern of GS staining in the liver surrounding the mass.
Results: The mean lesion size was 2.6 cm for NE, 3.0 cm for CC, 3.4 cm for FNH, and 6 cm for HCC. The mean fibrosis score was 1.6 for NE, 2.45 for CC, and 1 for HCC. 7/19 NE and 17/21 CC had some features of FNH surrounding the main lesion by H&E, including fibrous septa with bile ductules, aberrant vessels, and cholestatic features. However, only 1 NE and 1 CC case had both FNH features surrounding the metastatic lesion as well as map-like GS staining. All other NE as well as HCC and CC cases demonstrated hepatic perivenular staining similar to that observed in normal liver, regardless of FNH-like features on H&E. All 5 FNH exhibited map-like GS staining.
Conclusions: GS may assist in distinguishing true FNH from FNH-like mass effect. FNH is a malformation thought to develop secondary to abnormal blood flow; our study shows that although metastasizing lesions are often fibrogenic, may distort vasculature, and cause FNH-like features in the surrounding parenchyma, these do not represent true FNH in most cases. The infrequent case of a lesion surrounded by liver with both FNH features and GS map-like staining is likely a true FNH with a simultaneous occurrence of a second lesion.
Tuesday, March 5, 2013 9:30 AM
Poster Session III # 196, Tuesday Morning