Uterine lipoleiomyoma: a histopathological review of 17 cases

Lipoleiomyoma is a rare uterine tumor. The exact frequency and proliferation activity are not yet known. This study aims to know the frequency and evaluate the relation with renal angiomyolipoma. Lipoleiomyoma cases were immunohistochemically stained by antibodies for Ki-67, melanoma specific antigen HMB45, S-100 protein, and alpha smooth muscle actin (alpha-SMA). Frequency of uterine lipoleiomyoma among uterine myomatous tumor was 17/4904 (0.35%) in the Department of Human Pathology, Field of Oncology, Kagoshima University Graduate School database (1983-2003). Patients ranged from 45 to 74 years of age, and 10 cases were associated with leiomyoma. Six of 17 (35%) cases showed areas with renal angiomyolipoma-like vessels and atypical cellular features. Immunostaining was available in 12 cases. By Ki-67 labeling index, both muscle (average 1.38%) and fat (average 1.17%) portions of the tumor had greater proliferation than normal myometrium (average 0.76%), which suggests that fat portions of the tumor are proliferating adipose tissue rather than fatty degeneration of muscular counterpart. HMB45 antigen, which is positive in renal angiomyolipoma, was negative in three uterine cases having angiomyolipoma-like vessels (3/12). However, HMB45 antigen was positive in spindle-shaped tumor cells of three cases (3/12) which lacked angiomyolipoma-like vessels. Presence of angiomyolipoma-like blood vessels in these tumors is not an uncommon feature. However, the diagnosis of uterine angiomyolipoma should not be based on the result of HMB45 antigen immunoreactivity alone.