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Unusual Presentation of Focal Nodular Hyperplasia.

Clinical Nuclear Medicine: August 1995
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We report an unusual case of focal nodular hyperplasia presenting as a large tumor-like mass extending to the gastric pylorus. This showed increased activity on hepatobiliary imaging. Focal nodular hyperplasia usually develops in women of childbearing age (1). Although it may manifest clinically with vague abdominal pain and fullness, it typically is identified incidentally (1). The etiology of FNH remains unknown. However, regression has been documented after the discontinuation of oral contraceptives. Pathologically, the lesion consists of a nodular mass, frequently containing a central stellate scar with radiating fibrous septations (2). Histologic examination reveals an abnormal arrangement of hepatocytes, Kupffer cells, and bile ducts (2). Nuclear imaging reveals uptake of Tc-99m SC in 70% of cases because of the presence of Kupffer cells (3). Although rarely reported, two cases of hepatoblastoma showing uptake of Tc-99m SC have been noted in children (4). However, no known cases of hepatoblastoma have been reported to demonstrate both Tc-99m SC and HIDA uptake. These findings also assist in excluding hepatic adenomas from further clinical consideration (5,6). Sonographic evaluation reveals a nonspecific appearance, ranging from hypoechoic to hyperechioc (7). The size of individual lesions ranges from 1 cm to 20 cm, with multiple lesions being reported in 13% of cases (7). CT evaluation typically demonstrates a homogeneous mass of slightly decreased density, which becomes iso-to-hyperdense with intravenous contrast administration (7). A central fibrous scar is infrequently demonstrated on CT or ultrasound (3). This case emphasizes the potential of FNH to appear as a large tumor with extra-hepatic extension. It also supports the role of nuclear imaging when evaluating the etiology of a mass identified on CT or ultrasound.

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