During a year, myomas may undergo radical changes in their dimensions – from decreasing by 90% to growing by 200%. On average, myomas of the uterus increase in volume by 20–30% annually in the premenopausal period. On the other hand, myomas regress spontaneously in about 20% of women. After menopause uterine fibroids stabilize or regress. Every new or growing lesion of the uterus after menopause has to be diagnosed. There is no general definition of fast growing uterine myoma. The presence of fast growing uterine myoma, regardless of its definition, is associated with some clinical issues: it may become symptomatic (pain, bleeding, bulk symptoms), may be responsible for infertility, and a malignant process (leiomyosarcoma) may be present. Regardless of common belief, the risk of sarcoma is not related to the size of the uterus or its fast enlargement. The prevalence of sarcoma in myomas is 0.26%, and in rapidly growing myomas is 0.27%. Treatment should be individualized, selected for the age of the woman and her expectations (preservation of fertility, uterus), symptoms, size and localization of the myomas. The methods of surgical treatment of unsuspected “rapidly growing myomas” are the same as those of common uterine fibroids. Minimally invasive surgery is optimal, but a decision has to be made after evaluation of the risk factors of sarcoma.