Osteogenic sarcoma is highly unusual to affect the flat bones (thoracic spine and iliac bone). With your history of taking care of tuberculosis patient, your thoracic spine lesion can be tubercular affection (called as Pott's spine). Pott's spine is easily treatable disease with the medications.
Please feel free for your follow up questions.
I am afraid, there are no benign bone tumors mimicking the osteosarcoma.
It is privilege assisting you.