What is the most appropriate initial course of action?

An 18-year-old man presented to the thyroid clinic complaining of a lump in his neck that had been present for 9 weeks. It was not painful. At the age of 12, he had developed acute lymphoblastic leukaemia and had undergone a bone marrow transplant preceded by total body irradiation and cyclophosphamide.

On examination, he was euthyroid. There was a 1.5-cm firm mass on the left side of the neck, which moved when he swallowed.

Investigations:

serum thyroid-stimulating hormone1.9 mU/L (0.4C5.0)

serum free T416.8 pmol/L (10.0C22.0)

What is the most appropriate initial course of action?
A . CT scan of neck and thorax
B . FDG-PET-CT scan
C . surgical referral for hemithyroidectomy
D . technetium-99m scintigraphy scan of thyroid
E . ultrasound-guided fine-needle aspiration of the nodule