malignancy occurs in approximately 1% of thyroid nodules. papillary and/or mixed papillary/follicular carcinomas are by far the most common malignancy. the incidence is dramatically increased in post head/neck radiotherapy patients.
- papillary carcinoma 78%
- follicular lesion carcinoma 17%
- medullary carcinoma 4%
- anaplastic carcinoma 1%
- thyroid lymphoma – rare
- thyroid metastases – rare
a ‘cold nodule’ on nuclear medicine increases the suspicion of malignancy however the liklihood is still low.
sonographic signs increasing the suspicion of malignancy:
- solitary nodule
- hypoechoic
- punctate calcification have been reported as 95% specificity but a low sensitivity for diagnostic accuracy.
- irregular surrounding halo (blurred or incomplete)
- tall>wide
- irregular margins
- central vascularisation
- enlargement of a nodule
- large coarse calcifications and calcifications along the rim of nodule are common in all types of nodules and reflect previous hemorrhage and degenerative changes. it should be noted that some cancers may have been chronic but large and have undergone degenerative change. therefore, these nodules may demonstrate peripheral calcification and diagnostic aspiration biopsy may be appropriate to avoid missing a cancer .
- decreased internal echogenicity of a thyroid nodule with peripheral calcifications are in favor of malignancy. thus, thyroid calcifications as detected by sonography other than pin-point size provide little practical help in identifying cancer in the individual case.
- calcifications in a “solitary” nodule in a person younger than 40 years person should raise a strong suspicion of malignancy because of a relative cancer risk of 3.8 versus 2.5 in patients older than 40 years with calcified nodules. large calcifications are seen with increased frequency in medullary thyroid carcinoma .
importantly, a diagnosis of malignancy cannot be made without biopsy. again, keep in mind that the vast majority of thyroid nodules are benign.
see tirads for a nodule ‘suspicion’ grading system.