What is osteosarcoma primarily characterized as?

Osteosarcoma is primarily characterized as a hard-tissue sarcoma that typically affects the upper shaft of long bones, such as the femur, humerus, or tibia, as well as areas around the pelvis and knee. This type of cancer originates from osteoblasts, the cells responsible for bone formation, leading to the production of immature bone or bone-like tissue. Osteosarcoma primarily occurs in adolescents and young adults and is known for its aggressive nature and potential to metastasize, most frequently to the lungs.

The other options pertain to different types of tumors that do not align with the characteristics of osteosarcoma. Soft-tissue sarcomas, for instance, are distinct from osteosarcomas because they arise from connective tissues such as fat, muscle, or blood vessels, and benign tumors typically present less aggressive characteristics than those seen in osteosarcoma. Malignant skin cancer describes entirely different neoplastic processes focused on skin cells, further differentiating it from the bone-related pathology seen in osteosarcoma.