Myoid hamartomas of the breast are extremely rare breast lesions, with a poorly understood pathogenesis. A 60-year-old woman presented with a palpable mass in the right breast. Breast ultrasonography and mammography showed the presence of a breast lesion with benign characters, but were not diagnostic. A local excision of the mass was performed; histology revealed that the tumor was composed of epithelial and stromal cells. Histological and immunohistochemical findings established the diagnosis of myoid hamartoma. The patient is well 4 years later without tumor recurrence. Breast myoid hamartomas are exceptionally rare benign lesions; complete surgical excision achieves cure.