Primary Osteosarcoma of the Breast.

Extraskeletal osteosarcomas are extremely rare and account for < 1% of the soft tissue sarcomas. Most common site is in soft tissues of the lower extremities. Primary osteosarcomas of the breast are extremely rare and only a few cases have been reported in literature. It carries a very dismal prognosis in view of its high rate of local recurrence and distant spread. We report a case of primary osteosarcoma of the breast. A 44-year-old female presented with a 14 × 10 cm solid mass in right breast. She underwent wide excision and frozen section was consistent with metaplastic carcinoma. A possibility of malignant phyllodes tumor was kept therefore right axillary dissection was also done along with. Final histopathology was consistent with high-grade osteogenic sarcoma in view of haphazardly arranged spindle to stellate cells with presence of giant cells and a matrix showing osteoid and cartilaginous differentiation and on IHC tumor cells were positive for Vimentin, EMA, Pankeratin, and P 63 and negative for ER, PR, Her 2 neu, CK 7, CK 8/18, and CK 34. It is imperative to recognize this rare pathologic tumor variant in view of its need of multimodal management and overall poor prognosis. Immunohistochemistry plays an important part in establishing the diagnosis and hence the further management.