A bulge of osteosarcoma is a tumor mass. Osteosarcoma is a malignant bone tumor that is common in children and adolescents and can appear anywhere in the body. Osteosarcoma is mostly derived from malignant transformation of mesenchymal cells, and after the tumor volume reaches a certain size in the middle and late stages, there will be obvious localized lumps, i.e., enlarged tumor tissues, and accompanied by obvious pain. Osteosarcoma mostly occurs in the epiphyses of limbs, such as distal femur and proximal tibia. Early stage of osteosarcoma manifests as mild pain, middle and late stage of osteosarcoma may appear localized mass, generalized wasting and fever, etc., which can be determined through CT, pathological tissue biopsy, MRI and other examinations, and radical surgical resection can be adopted, and patients who cannot be operated need to undergo radiotherapy, chemotherapy and other comprehensive treatments. It is recommended to standardize the diagnosis and treatment under the guidance of specialists.