Let-7 expression was significantly decreased in leiomyosarcoma tissues, which may contribute to the malignant transformation of leiomyoma accompanied by overexpression of HMGA2 [15,16].Therefore, we postulated that the up-regulated miRs modify target molecules in addition to proliferation and differentiation of muscle cells and were associated with the development and growth of leiomyoma. The gene discussed is HMGA2; the disease is leiomyosarcoma.