Renal epithelioid angiomyolipoma: a rare variant with unusual behavior

To compare the clinical, pathological and oncological outcome of EAML with classic angiomyolipoma (AML).

A retrospective review of patients' files with a diagnosis of AML was conducted. Both classic and epithelioid AML were compared as regard the patients' demographics, mode of presentation, tumor features and follow-up data. The accuracy of preoperative radiological diagnosis of EAML and the postoperative pathological data were evaluated.

Between November 1988 and July 2012, 1,502 renal masses were treated. Forty-two patients (2.8 %) had renal AML of whom 12 patients (28.6 %) had epithelioid morphology. All the patients with EAML were symptomatic on presentation compared to 16.7 % asymptomatic patients with classic AML. Specific diagnosis of EAML was not suggested based on preoperative radiological evaluation. In one patient, there was a venous tumor extension into the right renal vein; another patient had a solitary pulmonary nodule. Pathological data of EAML patients showed wide areas of necrosis (4 patients), atypia (6 patients), increased mitotic figures (2 patients), nuclear anaplasia, enlarged nuclei and prominent nucleoli (3 patients), and multilobulated multinucleated giant cells (5 patients). At a median follow-up period of 12 and 9 months for EAML and classic AML groups, respectively, one patient with EAML had evidence of both local recurrence and distant metastasis 3 months following open radical nephrectomy.

Epithelioid AML is potentially aggressive and usually present as a symptomatic renal mass. It may be misdiagnosed as malignant renal mass on preoperative radiological evaluation.