How would you manage primary breast osteosarcoma?

Osteosarcoma of the breast is a rare and highly aggressive tumor, accounting for less than 1% of all primary breast malignancies. Due to its infrequent occurrence, there is a lack of prospective studies to determine the best treatment approach and most publications are case reports. Instead of focusing solely on breast localization, it is important to consider histology when establishing treatment options.

The first option would be excision with wide margins or mastectomy, and taking into account the histology subtype (osteoblastic, chondroblastic, fibroblastic, small cell, telangiectatic, high-grade surface), tumor volume, and margins decide for adjuvant treatment. I would recommend prioritizing adjuvant treatment with chemotherapy and cons...

For a de novo breast sarcoma including a malignant phyllodes tumor (with stromal overgrowth), depending on host factors (age, PS, organ function, etc.) and tumor factors (grade, size), the treatment options would include local therapy (preop XRT followed by WLE for low-risk tumors) or consideration for neoadjuvant systemic therapy followed by local Rx (for high risk tumors). For radiation-associated tumors, additional XRT is not recommended and the only adjuvant that can be used is systemic therapy. Doxorubicin-based regimens remain the SOC.