Intraparenchymal Breast Leiomyoma and Atypical Leiomyoma

Abstract Introduction: Intraparenchymal breast leiomyoma is a rare lesion of breast. The diagnostic criteria to differentiate benign and borderline breast leiomyoma was not yet clear. No atypical leiomyoma of breast parenchyma has been reported. Case series presentation: We described one case of leiomyoma and one case of bilateral atypical leiomyoma in breast parenchyma. The morphological features that lead to the diagnosis of atypical leiomyoma include invasive growth pattern, mild nuclear atypia and mitotic figures up to 3mitoses/10HPF. Conclusion Due to the limited experience, cases presented as atypical intraparenchymal breast leiomyoma should be closely followed.