Abstract
BackgroundHepatocellular adenoma (HCA) is conventionally considered a rare benign liver tumor, but advanced studies have revealed that HCA is heterogeneous, and may include a type that is prone to malignant transformations. Differentiation between well-differentiated hepatocellular carcinoma and focal nodular hyperplasia is necessary to diagnose hepatocellular adenoma through imaging; however, the tumor marker of hepatocellular carcinoma, protein induced by vitamin K absence, or antagonist II (PIVKA-II), is rarely positive in hepatocellular adenoma.Case presentationA 44-year-old woman presented to our hospital with complaints of loss of appetite and weight loss. Multidetector row computed tomography revealed a liver tumor (diameter, 80 mm) that was enhanced in the arterial phase. Her serum PIVKA-II level was very high (3327 mAU/mL). Based on the enlargement of the mass and the results of the diagnostic imaging, hepatocellular adenoma or hepatocellular carcinoma was suspected, and we considered the possibility of a malignant transformation due to the high level of serum PIVKA-II; thus, we performed hepatectomy. Histological examination showed brown pigment deposition in the hepatocytes, which was determined to be lipofuscin granules. Based on immunohistochemical findings, the diagnosis was unclassified hepatocellular adenoma. Immunohistochemical examinations revealed that the adenoma cells in the tumor were positive for PIVKA-II. Her serum PIVKA-II level returned to normal after the resection.ConclusionsWe present a case of unclassified hepatocellular adenoma with brown pigment deposition and elevation of serum PIVKA-II level. For the differentiation of liver tumors with high levels of PIVKA-II and hypervascular mass, hepatocellular adenoma should be considered.
Highlights
Hepatocellular adenoma (HCA) is conventionally considered a rare benign liver tumor, but advanced studies have revealed that HCA is heterogeneous, and may include a type that is prone to malignant transformations
Characteristic with immunohistochemical staining, the positive expression of liver fatty acid-binding protein (LFABP) in normal hepatocytes becomes negative in Hepatocyte nuclear factor 1α (HNF1α)-inactivated HCA
The unclassified type does not show a clear gene mutation or histologic characteristics, and cases are difficult to diagnose based on heavy bleeding and necrosis alone
Summary
The incidence of HCA in Western countries is 3–4 per 100,000 [3, 4]. In contrast, HCA is a very rare disease in Asia, in Japan. In this case, the serum level of PIVKA-II was very high, but it is usually negative in cases of HCA. Because of the low number of cases, we were unable to determine a clear association between high serum PIVKA-II level and malignant transformation, deposition of lipofuscin granules, and subtype classification. In HCC, the production PIVKA-II was believed to be caused by vitamin K insufficiency, vitamin K metabolic disorders, selective defects in the γ-carboxylase enzyme (which prevents the production of normal prothrombin), and/or cytoskeletal changes that impair vitamin K uptake as the hepatocytes undergo malignant transformation [26] We presented a case of unclassified HCA with brown pigment deposition and serum PIVKA-II level elevation. To differentiate liver tumors with high PIVKA-II levels and hypervascular masses by imaging, HCA should be considered
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