Osteosarcoma of the breast: a case report of a rare breast malignancy in a patient with prior partial mastectomy

Abstract

: Primary osteosarcoma of the breast (OSB) is a rare malignancy of the breast with poor prognosis. There are some reported cases of this infrequent malignant neoplasia, showing that in some instances it can be related to prior trauma or local irradiation in the area. Most malignant mesenchymal neoplasia can be found on the extremities, retroperitoneum, the trunk area and less common, breast, heart, thyroid and the lung. We present a 68-year-old female without any significant medical problems but with prior history of right breast cancer treated with partial mastectomy, adjuvant chemotherapy and local radiation in 2004, presenting to our breast clinic in 2020 with a palpable lesion and biopsy proven poorly differentiated malignant neoplasm, favoring poorly differentiated mammary carcinoma with osteoblastic giant cells. This patient went for a right total mastectomy with final pathology showing high grade osteoblastic osteosarcoma, requiring subsequent re-excision for positive margins. Here we discuss the recommended management and treatment for such a rare diagnosis, as currently no official treatment guidelines exist. We recommend wide local excision without lymph node biopsy and adjuvant chemotherapy. Radiation may be an option but should be decided upon on a case by case basis given the lack of data on its efficacy.