Epithelioid angiomyolipoma of the kidney: CT and CEUS characteristics and clinical outcomes

Objective: To review the computed tomography (CT) and contrast-enhanced ultrasonography (CEUS) features and clinical outcomes of renal epithelioid angiomyolipomas (EAMLs). Materials and methods: Seventeen patients diagnosed with EAML from January 2004 to June 2015 at the Second People’s Hospital of Lianyungang and Nanjing Drum Tower Hospital were included. All of the patients underwent CT, and six underwent CEUS. Patient demographics, outcomes, imaging characteristics and pathologic features were determined by chart review. Results: The patients included seven women and ten men with a mean age 45.7 (range, 23-62) years. Only two patients had tuberous sclerosis complexes (TSCs). Seven patients presented with flank pain, one presented with acute bleeding, and nine were asymptomatic. Nine patients underwent radical nephrectomy, and eight patients underwent partial nephrectomy. The mean follow-up period was 28.5 (range, 2-126) months, and fifteen patients were alive with no evidence of disease at the time of the last follow-up, one patient exhibited local recurrence and lung metastases, and another patient developed distant metastasis. The mean maximal tumor diameter was 6.1 (range, 1.2-12.5) cm. The fat components of two lesions were detected by CEUS and one by CT. On unenhanced CT, the intratumoral attenuations were hyperattenuating in nine patients, isoattenuating in one patient and hypoattenuating in seven patients. The contrast enhancement degree was mild in one patient, moderate in six patients and marked in ten patients. The contrast enhancement pattern was homogeneous in eight lesions and heterogeneous in nine lesions. On CEUS analysis, two lesions were found to be homogeneous, and four were heterogeneous. Tumor necrosis was observed in six cases, five of which had a maximal tumor diameter ≥ 10 cm, and hemorrhaging was present in three cases. All patients were positive for melanoma (twelve were positive for HMB45, three were positive for melan A, and two were positive for both). Conclusions: Renal EAML can have a range of imaging appearances. Our data suggested that the majority of the tumors (size < 10 cm) were solid and had a tendency to be hyperattenuating on unenhanced CT images. Hemorrhaging or necrosis was observed in tumors with sizes ≥ 10 cm with heterogeneous enhancement. Regarding CEUS appearances, the uniform lesions were hypervascular and homogeneous, whereas the lesions that contained hemorrhaging, necrosis or fat components were heterogeneous. In contrast to classic AML, which is benign, EAML is potentially malignant and exhibits aggressive clinical features, including local recurrence and distant metastasis.