Benign metastasizing leiomyoma (BML) is a rare disease characterized by extrauterine benign leiomyomatosis in patients with a previous or concomitant history of uterine leiomyoma. Currently, there are no specific criteria to predict the metastasizing ability of the uterine leiomyoma and the risk of malignant degeneration of pulmonary BML, and these are the aims of this study. We analyzed 10 uterine (three leiomyomas, four leiomyomas that gave rise to lung BML, three healthy tissues) and 11 pulmonary tissue samples (eight lung BML, three healthy tissues). Interestingly, one of the BML lesions exceptionally evolved into a leiomyosarcoma (case 2). Uterine leiomyoma microvascular density (MVD) was higher in the patients with uterine leiomyomas that gave rise to lung BML, reaching a peak in case 2. Strong positivity for the estrogen (ER) and progesterone (PR) receptors and a low proliferation index (Ki67 < 1%) were discovered both in patients with uterine leiomyoma and in patients with BML. Interestingly, in case 2, the last dedifferentiated leiomyosarcoma showed a weaker ER and PR positivity with a higher proliferation index (Ki67:30%). Regarding the uterine miRNA-126, a trend toward a hypo-expression between uterine leiomyoma and uterine leiomyoma that gave rise to lung BML was discovered, reaching the lowest level in case 2. Considering the pulmonary samples, we observed a higher miRNA-221 and a lower miRNA-126 expression in the leiomyosarcoma. We tried to better elucidate the biological behaviour of this rare disease. The analysis of the miRNA-221 and miRNA-126 could offer new diagnostic, prognostic and therapeutic perspectives.
Keywords: Benign metastasizing leiomyoma; Surgery; Uterine leiomyoma; miRNA.