Postoperative assessment after thyroid cancer surgery is performed in the surgical bed and regional lymph nodes, looking for possible recurrence of disease.
Radiographic features
Ultrasound
usually performed in the first 6-12 months, and then as needed by the patient's risk factors 1
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suspicious lymph nodes are biopsied with fine needle aspiration (FNA)
thyroid cells in the node indicate a metastasis
if the FNA is non-diagnostic, an assay for elevated thyroglobulin in the sample will indicate a metastasis
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~34% of postoperative patients have small thyroid bed nodules 2
rate of growth is slow, and 81% do not increase in size over three years
only 33% of malignant nodules show interval growth
CT
Ultrasound is the first-line modality for evaluation of the postoperative neck. CT may be useful in certain situations 4:
bulky and widely distributed recurrent nodal disease, where ultrasound may not completely delineate disease
assessment of possible invasive recurrent disease where potential aerodigestive tract invasion requires complete assessment
when neck ultrasound is felt to be inadequately visualizing possible neck nodal disease (e.g. high thyroglobulin, negative neck US)
When CT is employed in follow-up, this is often performed without contrast in the early post-operative period if radioiodine ablation has not been performed, since iodinated contrast can compete with radioiodine treatment for uptake. If a study with IV contrast is necessary, radioiodine can be administered 4–8 weeks following the injection of contrast medium 5.
Differential diagnosis
scar fibrosis: often more linear in shape
postoperative / traumatic neuroma
residual thyroid tissue