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The information provided here is not complete enough to give you specific medical advice.
Symptoms like persistent fever, weight loss, loss of appetite, night âsweats along with multiple enlarged, painless lymph ââânodes may indicate conditions like âcancerâ.
A 3.5 cm mass can either originate from the bone, cartilage, the neural structures or the soft tissue (muscles or fat tissue) associated with the rib cage.
A complete and detailed description of the CT report (including density of the structures) will help to determine the origin of the mass.
It would be recommended that you consult your doctor who can clear your doubts for you.
I hope this helps.