RESUMO
INTRODUCTION: Benign Osseous metaplasia of the breast is rare, with only a few cases reported in the literature. Here we present a case of benign osseous metaplasia of the breast presenting as a breast lump. CASE PRESENTATION: 38-year-old previously well woman presented with a one-year history of bilateral breast pain and a left-sided breast lump. Ultrasound and mammography suggested calcified fibroadenoma. An ultrasound-guided true cut biopsy revealed fibrous tissue containing foci of adenosis in the presence of a myoepithelial cell layer. Excision biopsy was performed, and histopathological examination showed bone matrix deposition occupying most of the nodule with peripheral hyalinized tissue but no evidence of malignancy. A diagnosis of benign osseous metaplasia of the breast was made, and the patient recovered well without recurrence after lump excision. DISCUSSION: Only a few cases of osseous metaplasia are reported in the literature. Most reported cases are malignant, such as in fibrosarcoma, malignant mesenchymoma, osteoid sarcoma, osteogenic sarcoma, and osteochondrosarcoma.Very few cases of osseous sarcoma are reported in benign lesions such as fibroadenoma, pleomorphic adenoma, benign mesenchymoma, phyllodes tumor, and amyloid tumor of the breast. Joshi et al. first reported a case of benign osseous metaplasia of the breast presenting as breast lump in an HIV-positive patient [18]. We, therefore, consider this case to be the second case report of benign osseous metaplasia of the breast presenting as a breast lump, but the patient had no chronic illness. CONCLUSION: A breast lump can be the first presentation of benign osseous metaplasia.