Clinicopathological analysis of 156 patients with angiomyolipoma originating from different organs

Angiomyolipoma (AML) is a benign mesenchymal tumor composed of variable proportions of adipose tissue, spindle and epithelioid smooth muscle cells and abnormal thick-walled blood vessels. Approximately one-third of epithelioid AML (EAML) cases have been reported to have metastasis. Thus, it would be of interest to identify the adverse pathological parameters correlated with outcome. However, few studies have been conducted on large numbers of samples. The aim of this study was to highlight the clinicopathological features of AML and the morphological features of EAML, which were correlated with malignant behaviors in patients from a single institutional series analysis. One hundred and fifty-six consecutive AMLs, correlating with pathological characteristics, were analyzed between 1981 and 2010. The Chi-square test was performed to clarify the significance of the clinicopathological factors among the regular and epithelioid subtypes with or without atypia. The two organs most commonly involved were the kidney (77%, 120/156) and liver (14%, 22/156). Of the 156 AMLs, EAMLs (17.3%, 27/156) had more marked mitosis, hemorrhage and multinucleated giant cells compared with the regular AMLs (82.7%, 129/156). The 11 EAMLs with atypia (40.7%, 11/27) had more nucleoli and mitotic cells compared with the 16 EAMLs without atypia (59.3%, 16/27; p<0.05). Follow-up results of 79% of cases (124/156) were obtained, and of these, only one kidney AML (0.8%, 1/124) presented with liver metastasis one year after nephrectomy. This sizeable single institutional AML series analysis revealed that the kidney and liver were the two most commonly involved organs, and most of the cases presented a benign clinical course. Few EAMLs were malignant, although adverse features including atypical mitotic figures, blood vessel invasion and tumor embolus may be significant in predicting malignant behavior.