Leiomyoma with Bizarre Nuclei: A Stagnant Precursor to Leiomyosarcoma?

Leiomyoma with bizarre nuclei (LM-BN) is a rare uterine smooth muscle tumor characterized by a remarkable nuclear atypia reminiscent of its malignant counterpart leiomyosarcoma (LMS). While it presents with an overall benign clinical course, the biological nature and pathogenesis of LM-BN remains largely unknown. The controversy about the relationship between LM-BN and benign and malignant uterine smooth muscle tumors remains unresolved. To date, the diagnosis of LM-BN relies mainly on morphological characteristics, and no effective molecular markers have been established. Here we describe and summarize recent progress in understanding this unique tumor entity, with a focus on new findings regarding molecular and genomic alterations and the potential relationship of LM-BN with LMS.