We studied retrospectively the clinical, radiological and pathological records of 10 patients with hepatic AML, who were referred to our hospital between 2004 and 2007. There were three male and seven female patients with a mean age of 55.1 years (range, 19-78 years). Four were asymptomatic and were found incidentally upon general health examination. Two had complained of upper abdominal pain. Four had symptoms of unilateral flank pain. Previous medical history showed nephrectomy for renal AML in three patients, and recurrent pneumothorax and hydrothorax in one. Physical examination presented multiple miliary russet papilla on the face and several periungual fibromas in four patients. Renal ultrasound demonstrated unilateral renal AML in three patients who had a previous history of nephrectomy, bilateral multiple renal AML in one, and intratumoral hemorrhage in three. Laboratory analysis showed normal liver function and serum α-fetoprotein in all 10 patients.

MSCT was adopted for all 10 patients, using a 16-slice computed tomography (CT) scanner (Lightspeed, GE Healthcare, USA). The scan parameters included a section thickness of 5 mm, pitch of 1.375:1, reconstruction thickness of 1.25 mm, and field of view of 248 mm × 330 mm. Intravenous contrast material [60-120 mL iopamidol (Isovue 370); Bracco Diagnostics, Princeton, NJ, USA] was used in all patients. Enhanced CT was performed in the arterial phase, portal venous phase, and delayed phase with a delay time of 26, 70 and 120 s since the injection of intravenous contrast material, respectively. All imaging studies were reviewed retrospectively by the same radiologist with over 15 years experience in abdominal CT studies.

Ultrasound-guided biopsy of hepatic nodules was adopted in six patients, with an 18-gauge needle. Left hemihepatectomy was performed in two patients. Microscopical examination of the specimens was performed with routine HE staining. Immunohistochemical studies were carried out on the specimens.

There were six patients with sporadic hepatic AML. The diagnosis of hepatic AML was confirmed by liver biopsy in four patients and partial liver resection in two.

Four patients with hepatic AML had associated TSC, the diagnosis of which was based on its revised criteria[3]. The diagnosis of hepatic AML was established by biopsy of the hepatic fat-deficient nodules in two patients. In another two case, the diagnosis of hepatic AML was based on the detection of fatty density in multiple hepatic nodules[4]. In one patient with hepatic AML and TSC, the diagnosis of lymphangioleiomyomatosis (LAM) was based on the typical imaging features of multiple, thin-walled lung cysts, hydrothorax and enlarged periaortic lymph nodes.

Six patients with sporadic hepatic AML had solitary fat-containing masses with a mean size of 45 mm (size range, 10-80 mm) in the liver. On dynamic contrast-enhanced CT, the non-fat component of the lesions showed heterogeneous hyperdensity in the arterial phase and portal venous phase, and heterogeneous isodensity in the delayed phase, in comparison to the surrounding liver in five patients, (Figure 1A and B). Three had marked intratumoral vessels in the arterial and portal venous phases.

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Figure 1 Patient with sporadic hepatic angiomyolipoma. A: Enhanced CT showed one well-defined, fat-containing nodule with prominent central vessels in the arterial phase; B: Enhanced CT showed sustained contrast enhancement of the intratumoral non-fat component in the portal venous phase.

Four patients with hepatic AML and TSC had multiple, well-circumscribed hepatic nodules ranging from 2 to 40 mm (mean size, 8 mm) in the peripheral liver. Most of the nodules contained definite fatty density, and their non-fat components were enhanced mildly to markedly after administration of intravenous contrast material. Seven fat-deficient nodules were found in two patients (Figure 2A). On dynamic contrast-enhanced CT, the non-fat-containing nodules presented with heterogeneous high density in the arterial phase, mild hypodensity in the portal venous phase, and hypodensity in the delayed phase. Distorted intratumoral vessels and dilated feeding arteries were found in two of the seven nodules (Figure 2B-D). Except for multiple fat-containing nodules in the liver parenchyma, one sheet-like lesion in the right portal vein and several enlarged periaortic lymph nodes were noted in one patient (Figure 3A and B). Multiple thin-walled lung cysts and hydrothorax had been demonstrated previously by chest CT (Figure 3C).

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Figure 2 Patient with hepatic angiomyolipoma and TSC. A: Plain CT showed two fat-containing nodules in the right liver lobe, and one unenveloped fat-deficient nodule in the left liver lobe; B: Enhanced CT showed a fat-deficient nodule with marked hyperdensity, with intratumoral vessels in the arterial phase; C: Enhanced CT showed a fat-deficient nodule with mild hypodensity, with prominent central vessels in the portal venous phase; D: Enhanced CT showed a fat-deficient nodule with homogeneous hypodensity in the delayed phase; E: Microscopic examination demonstrated vacuolated lipocytes, blood vessels and scattered epithelioid cells with eosinophilic cytoplasm and peripherally located nuclei (HE, original magnification × 40).

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Figure 3 Patient with TSC and hepatic angiomyolipoma and LAM. A: Enhanced CT showed multiple fat-containing nodules in the liver; B: Enhanced CT showed an intra-portal-venous lesion and several enlarged periaortic lymph nodes; C: Chest CT showed multiple, thin-walled lung cysts and right hydrothorax.

Histopathological examination of the specimens showed various amounts of vacuolated lipocytes, blood vessels and scattered epithelioid cells with eosinophilic cytoplasm in all eight patients with liver biopsy or partial liver resection (Figure 2E). Immunohistochemistry demonstrated tumor cells with cytoplasm positive for HMB-45 in all eight patients.

Hepatic angiomyolipoma (AML) is a rare benign mesenchymal neoplasm. It can occur sporadically or in conjunction with tuberous sclerosis complex (TSC). Definitive preoperative diagnosis of hepatic AML is important because of its benign nature and it should not be resected. It is still a difficult condition for the radiologist and clinician.

The correlation between hepatic AML and its clinical setting has not been reported often in the literature. The imaging features of hepatic AML vary. Fat-deficient hepatic AML has been reported with increasing frequency in recent times. It is difficult to differentiate from hepatocellular carcinoma.

This study emphasized that imaging features of hepatic AML are related closely to its clinical setting. Multiple hepatic AMLs, with or without a fat component, are characteristic of TSC. When coexisting intravascular lesions and hepatic AML are detected in patients with TSC, lymphangioleiomyomatosis (LAM) should be considered. Hepatocellular carcinoma must be suspected when hepatic non-fatty nodules are detected in hepatitis B carriers with TSC.

This study serves as a reminder of the imaging features of hepatic AML in patient with or without TSC. This study is limited by its retrospective nature and small number of patients, and a large sample study should be undertaken in the future.

TSC is an autosomal dominant genetic disease characterized by the growth of hematomas in multiple organs. LAM is a rare disease that is characterized by disorderly smooth muscle proliferation throughout the bronchioles, perivascular spaces and lymphatic system.

The authors studied the dynamic computed tomography features of hepatic AML in patients with or without TSC. This study was well performed and will be of interest to readers.