Benign metastasizing leiomyoma (ICD.0 8898/1) is a rare phenomenon characterized by multiple benign smooth muscle tumors (metastases) in the organs and tissues of patients with uterine leiomyoma without evidence for another tumor process. This tumor should be differentiated from leiomyosarcoma, at the same time account must be taken of the fact that its morphological criteria are not always effective. Molecular genetic testing is a more accurate method that allows valid differentiation of leiomyoma from leiomyosarcoma. Genetic testing is used to estimate losses of heterozygosity and microsatellite instability, which are characteristic of leiomyosarcoma only. The paper describes a clinical case of benign metastasizing leiomyoma in a 54-year-old patient with uterine myoma and pelvic lymph node metastasis. Molecular genetic testing was carried out using the samples obtained from primary uterine leiomyoma, morphologically altered ovarian tissue, and lymph node metastasis to determine the common origin of tumors in the uterus and lymph node and to reveal the benign or malignant nature of these neoplasms. Despite the fact that the term "benign metastasizing leiomyoma" is widely accepted in the world literature, neither these tumors nor metastases have morphological or genetic signs of malignancy so we consider the term "systemic leiomyomatosis" to better reflect the essence of this process.