Primary osteosarcoma of the breast after complete resection of a metaplastic ossification: a case report

BACKGROUND Primary osteosarcoma of the breast is an extremely rare lesion. The pathogenesis of primary osteosarcomas is controversial. CASE PRESENTATION We present the case of a 63-year-old white German woman who presented with a mass in her right breast after routine screening. The core needle biopsy showed ductal hyperplasia with metaplastic ossification of the breast tissue. Complete excision of the lesion with standard safety margins was performed. The final diagnosis was metaplastic ossification. Three years later, our patient presented again with a painless lump in her right breast about 15 × 8 × 7 cm, extending to the lower part of axilla with skin ulceration. Pathologic diagnosis was osteosarcoma. Positron emission tomography and computed tomography and staging showed no other lesions. Modified radical mastectomy and axillary lymph node dissection was performed, no lymph node metastases were found. CONCLUSIONS Our case highlights the possibility that primary osteosarcoma of the breast may develop after complete resection with the classical safety margin for metaplastic ossification. Long-term follow-up after resection of this benign breast lesion is required.