A 19-year-old woman presented to her family physician with sharp right flank pain during deep inspiration or twisting of the upper body. An abdominal ultrasound showed a large mass in the right lobe of the liver. On contrast-enhanced computed tomography (Fig. 1A-C), a slight arterial enhancement was found in the center of the lesion (Fig. 1B), which was more pronounced during the portal venous phase (Fig. 1C). History and physical examination revealed a regular intake of an oral contraceptive (ethinyl estradiol and desogestrel), a subclinical hypothyroidosis, and a body mass index of 25 kg/m2. Aside from a mildly elevated gamma glutamyl transpeptidase level, liver tests and tumor markers were all normal.
The histopathological investigation of a diagnostic ultrasound-guided liver biopsy and the following hepatic lobectomy showed a replacement of liver parenchyma by loose myxoid mesenchymal stroma with a proliferation of abnormal bile ducts. Only residual cords and islands of hepatocytes were embedded in the lesion (Fig. 2A-C). The tumor was completely removed (marginal resection).
Mesenchymal hamartoma of the liver (MHL) is a benign liver tumor with a poorly understood pathogenesis.1, 2 Although rare, it is the second most common benign liver tumor in children, encompassing 3%-8% of all childhood liver tumors.3 The vast majority of MHLs are diagnosed before the first 5 years of life3 and they are rarely seen in adults. MHL can sometimes even be recognized in utero.1 Usually, the lesion grows as a painless mass of the right lobe and symptoms are related to large tumor size. The majority of MHLs are cystic tumors, but some MHLs are solid.3-5 Imaging findings on contrast-enhanced computed tomography are absence of a tumor capsule and a weak heterogeneous enhancement in solid areas, which is nonspecific but different from liver adenomas and focal nodular hyperplasia4 (Table 1). Thus, the clinical diagnosis of MHL is quite challenging, especially in adult patients (Table 1). The histopathology of this lesion is usually straightforward and is characterized by a lack of a fibrous pseudocapsule of the tumor, the replacement of the liver parenchyma by loose fibrous or myxoid stroma, the occurrence of irregular bile ducts, and the detection of cords or islands of residual hepatocytes, especially at the periphery.1, 3, 5 Hepatic lobectomy or enucleation is the treatment of choice. Recurrences of MHL are unusual.
|Diagnosis||Clinical Features||Enhanced Computed Tomography Imaging|
|Hemangioma||Usually incidental finding, hemorrhage, large size.||Characteristic pattern. Early peripheral enhancement with centripetal progression and late uniformly enhanced tumor.|
|Focal nodular hyperplasia||Usually incidental finding, most common in young women, occasional steroid use, AFP- negative. Background liver normal.||Characteristic bright enhancement at late arterial phase, returns to normal in portal phase. Delayed enhancement of the central scar.|
|Hepatic adenoma||Almost exclusively women, steroid use, AFP- negative. Background liver normal.||Heterogeneous due to hemorrhage and necrosis. Early enhancement, appears isoattenuating relative to the liver on delayed scans.|
|Nodular regenerative hyperplasia||Diffuse involvement of the liver (size 0.1-1.0 cm) AFP-negative. Background liver normal. Association with portal venous obstruction.||Not specific. Hypoattenuating nodules may be present.|
|Focal fatty changes||Usually incidental finding. Association with obesity, diabetes, malnutrition, and alcoholic hepatitis. Background liver normal.||Hypodense nodule that enhances but remains hypodense in relation to the surrounding liver parenchyma.|
|Intrahepatic bile duct adenoma or hamartoma||Usually incidental finding. Mainly in subcapsular areas (usual size < 1.0 cm).||Small well-defined hypoattenuating or isoattenuating lesion with little if any enhancement.|