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I have gone through the images (attachment removed to protect the patient's identity) that you have provided, and quite clearly, there is an enlargement of the thymus, having a sort of bulged-out outline than concave. However, if you would upload them, I could have compared these with your previous CT (computed tomography) images. Nonetheless, an enlarged thymus has not taken up much contrast, nor has any calcification, cystic, or necrotic change, or invasion (those are good signs). The concept of thymic rebound is that the naturally shrunken thymus regrows in patients having steroid therapy, chemotherapy, etc. Have you been on any such regimen? It may simply be a rebound and may not require any further action. But if not, then benign thymic neoplasm, that is, the tumor would be the first consideration. In that case, your doctors may suggest you get a biopsy for confirmation, staging, or directly proceed to treatment options, which may involve surgery, radiotherapy, chemotherapy, etc. They may also think of a chest MRI (magnetic resonance imaging), where a thymic rebound would show a chemical shift and a tumor would not. So at this stage, you need to get back to your treating doctors and follow their advice. If you prefer to, you can upload a previous CT to make a comparison with the new scan (not very urgent, though). Lastly, whatever "jagged area" you noticed maybe an artifact or other technical issue unrelated to our physiology or disease. So, ignore it.
I hope you get well soon.
The Probable causes:
Thymoma.Investigations to be done:
FNAC (fine needle aspiration cytology), Biopsy, and MRI (magnetic resonance imaging).Differential diagnosis:
Thymic rebound.Probable diagnosis:
Excision.Regarding follow up:
With previous images, if comparison is required.