Osteosarcomas are usually found because of the symptoms they are causing
Bone pain and swelling
Pain at the site of the tumor in the bone is the most common symptom of osteosarcoma. The most common sites for these tumors in younger people are around the knee or in the upper arm, but they can occur in other bones as well. At first, the pain might not be constant and might be worse at night. The pain often increases with activity and might result in a limp if the tumor is in a leg bone.
Swelling in the area is another common symptom, although it might not occur until later. Depending on where the tumor is, it might be possible to feel a lump or mass.
Limb pain and swelling are very common in normal, active children and teens. They are much more likely to be caused by normal bumps and bruises, so they might not prompt a doctor visit right away. This can delay a diagnosis. If your child has these symptoms, and they don’t go away within a few weeks (or they get worse), see a doctor so that the cause can be found and treated, if needed.
These symptoms are less common in adults, so they should be a sign to see a doctor even sooner.
While pain and swelling are often the earliest and most common signs of osteosarcoma, this malignancy can cause a number of other symptoms, including:
A bump, depending on where the tumor is located
Redness and warmth at the site of the tumor
Unexplained weight loss
Bone fractures (breaks)
Although osteosarcoma might weaken the bone it develops in, fractures (breaks) are not common. Exceptions are rare telangiectatic osteosarcomas, which tend to weaken bones more than other forms of osteosarcoma and are more likely to cause breaks where the tumor is.
People with a fracture next to or through an osteosarcoma often describe a limb that was sore for a few months and suddenly became very painful when the fracture occurred.