Definition:

Uterine leiomyoma, also known as fibroid, is the most common benign neoplasm of the female genital tract. It is a discrete, round, firm, often multiple uterine tumor composed of smooth muscle and connective tissue. The findings derived from high-throughput sequencing combined with previous knowledge have led to an emerging molecular classification of leiomyomas, suggesting that there are several distinct pathogenic pathways involved in leiomyoma formation. The evidence points to at least 4 molecular subclasses: leiomyomas with MED12 mutation, FH inactivation, HMGA2 overexpression, and COL4A6-COL4A5 deletion. While it is thought that the initial events that trigger leiomyoma tumorigenesis involves somatic mutations, it is evident that the development and growth of leiomyoma are highly dependent on ovarian steroid hormones, in particular, progesterone.