A case of extraskeletal osteosarcoma with metastasis to the skin.

We present an 83-year-old woman with extraskeletal osteosarcoma (ESOS) of the breast who developed metastasis to the scalp. Skeletal osteosarcoma is the most common primary malignant neoplasm of the bone, predominantly occurring in the metaphysis of the long bones of adolescents and young adults. ESOS, in contrast, occurs primarily in the fifth and sixth decades of life, most commonly in the soft tissue of the thigh.