thyroid pathology
malignant v's benign
there is no single ultrasonographic feature to distinguish between the two. features to assist in differentiating include:
cystic v’s solid
- rare to have just a pure epithelial cyst
- nodules which contain a cystic component nearly always have a solid component.
- they are benign lesions which have undergone cystic degeneration or haemorrhage.
- however, papillary carcinoma can also have a cystic component.
single v’s multinodularity
- multinodularity does not indicate all are benign.
- comet tail sign usually signifies a thyroid colloid nodule.
hypoechoic v’s hyperechoic
- generally hyperechoic are benign ,usually malignant tumours are hypoechoic or isoechoic.
halo
- the margin of a nodule with a halo effect is usually benign however this has also been described in some malignant lesions
- so this is not a reliable indicator
macro v’s microcalcification
- can be a good indicator of benign nodules if macrocalcification
- microcalcification is described in many malignancies
vascularity
- not a good indicator.
multinodular goitre
most thyroid nodules have a more hypoechoic ultrasound appearance than normal thyroid tissue and a few are more hyperechoic.
a sonolucent rim, which is called a halo may be present around a nodule. this represents a capsule or another interface, such as inflammation or edema, segregating the nodule and the rest of the gland.
doppler technique may demonstrate increased vascularity within a nodule or a halo.
ultrasound image- an oedematous enlarged thyroid.
ultrasound image- multi-nodular goitre
nodules are not a single disease but are a manifestation of different diseases including adenomas, carcinomas, inflammations, cysts, fibrotic areas, vascular regions, and accumulations of colloid.
thyroiditis
there are a variety of auto-immune thyroid conditions.
- hashimoto’s thyroiditis
- graves disease
- de quervain’s subacute thyroiditis
- acute suppurative thyroiditis
the most commonly encountered are hashimoto’s thyroiditis and graves disease.
graves disease
an auto-immune disease causing hyperthyroidism and thyrotoxicosis. patients often have exophthalmus (bulging eyes) it can be associated with a’polyglandular’ spectrum.
on ultrasound, the gland will be enlarged, usually heterogeneous and markedly hyperaemic.
it is so hypervascular, the colour doppler appearance has been described as a “thyroid inferno”.
grave’s opthalmopathy:
typical prominant eye protrusion caused by swelling of the eye muscles affected by the thyroid auto-antibodies.
ultrasound image- graves disease- hyperaemic (“thyroid inferno”)
hashimoto’s thyroiditis
- also an autoimmune disease.
- slow onset of hypothyroidism.
- on ultrasound:
- a heterogeneous gland
- initially enlarged, becoming atrophic over time.
transverse ultrasound image of the thyroid with early hashimoto’s thyroiditis.
the thyroid is normal in size with pseudonodular change starting to develop.
images courtesy of callum linehan.
ultrasound image – a thyroid with early hashimoto’s thyroiditis. heterogenous and pseudo-nodular changes developing.
colour doppler image – early hashimoto’s thyroiditis, vascularity is mildly increased.
transverse ultrasound image of an enlarged thyroid with progressed hashimoto’s thyroiditis.
the thyroid is enlarged and heterogenous with diffuse a pseudonodular appearance.
images courtesy of callum linehan.
ultrasound image – a thyroid with progressed hashimoto’s thyroiditis. note the linear echogenic striations – these are a specific sign of hashimoto’s thyroiditis in addition to the pseudonodular texture.
colour doppler image – progressed hashimoto’s thyroiditis. no hyperaemia.
transverse b-mode image of an atrophic thyroid with advanced hashimoto’s thyroiditis.
note the diffuse pseuodonodular texture with linear echogenic striations representing lymphocytic infiltration and fibrosis.
images courtesy of callum linehan.
ultrasound image – an atrophic thyroid lobe with advanced hashimoto’s thyroiditis.
case courtesy of callum linehan.
colour doppler image – reduced vascularity.
de quervain's subacute thyroiditis
transverse ultrasound image of a thyroid.
the left lobe is enlarged and heterogenous compared to the right. tender to probe pressure corresponding with the patient’s region of pain.
longitudinal ultrasound image of a thyroid with de quervain’s thyroiditis.
irregular ill-defined hypoechoic areas are representative of lymphocytic infiltration after an infection (e.g. influenza).
transverse ultrasound image of a thyroid with de quervain’s thyroiditis.
highlighted anatomy. note the irregular hypoechoic areas are without mass affect and interlinked – different to true nodules.
images courtesy of callum linehan.
transverse colour doppler image of a thyroid with de quervain’s thyroiditis.
the enlarged tender gland demonstrates increased vascularity.
image courtesy of callum linehan.
thyroid malignancy
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.
papillary carcinoma
ultrasound image- papillary carcinoma-the red dots illustrate the punctate microcalcifications. these generally will not cast an acoustic shadow because of their size.
transverse image of papillary carcinoma
colour doppler of the same lesion.
rounded lesion in the superior portion representing a confirmed papillary carcinoma.
some shadowing from the internal calcification is shown here however this is not common.
follicular carcinoma
ultrasound image – thyroid follicular carcinoma.
a solitary well-circumscribed hypoechoic and vascular nodule.
image courtesy of callum linehan.
b-mode and colour doppler image of a follicular carcinoma demonstrating internal vascularity.
images courtesy of callum linehan.
ultrasound image – transverse thyroid, a large infiltrative follicular carcinoma occupies most of the right thyroid lobe.
image courtesy of callum linehan.
longitudinal b-mode and colour doppler image using a curvilinear probe.
the curved probe provides a wide and deeper field of view for cases with a large thyroid mass or retrosternal extension.
the diffuse lobe involvement and features of this follicular carcinoma are better appreciated.
note the irregular margins and vascularity.
images courtesy of callum linehan.
parathyroid adenoma
- the parathyroid glands are usually on the peripheral surface of the thyroid. they are usually paired superiorly and inferiorly but have a variety of locally ectopic positions. on ultrasound, the normal parathyroids are not generally visible.
- the parathyroid glands regulate calcium levels. the clinical manifestation is usually hypercalcaemia.remember the symptoms: stones, bones, groans, and psychic overtones.
ultrasound image- the parathyroid glands regulate calcium levels. the clinical manifestation is usually hypercalcemia.remember the symptoms: stones, bones, groans, and psychic overt.
ultrasound image-parathyroid adenoma the parathyroid glands are usually on the peripheral surface of the thyroid. they are usually paired superiorly and inferiorly but have a variety of locally ectopic positions.
transverse ultrasound image of a parathyroid adenoma.
presents as a well-circumscribed ovoid inhomogeneous hypoechoic lesion at the posterior peripheral upper pole margin.
image courtesy of callum linehan.
longitudinal b-mode and colour doppler image of a parathyroid adenoma.
demonstrates the internal vascularity of the adenoma and upper pole position (which can vary).
images courtesy of callum linehan.
other neck masses
more commonly encountered neck masses include:
- lymphadenopathy
- branchial cleft cysts
- thyroglossal duct cysts
- soft tissue tumour such as lipomas, squamous cell carcinomas (scc) and sarcomas.
branchial cleft cyst
results from the failure of closure of the 2nd branchial cleft (at approximately 7 weeks). these are the ‘gill slits’ on the embryo thus branchia from the greek meaning “gills”. may not present until early adulthood.
on ultrasound there will be a para-sagittal cyst with low level echoes. it will be stationary during swallowing. because they may spontaneously rupture or have a pharyngeal fistula, the cyst may be transient in nature.
ultrasound image- a branchial cleft cyst. may be transient in nature.
ultrasound image- the branchial cleft cyst may be rounded but is more often ovoid
ultrasound image- the same branchial cleft cyst superficial to the jugular vein and right lobe of thyroid, in transverse.
ultrasound image- branchial cleft cyst superficial to the jugular vein and right lobe of thyroid.
ultrasound image of a brachial cleft cyst positioned between the submandibular and parotid gland.
image courtesy of callum linehan.
b-mode and colour doppler image of a brachial cleft cyst.
it contains homogenous hypoechoic fluid and thin walls. colour doppler demonstrates ‘pseudo-flow’ caused by movement of fluid under the influence of the ultrasound beam.
images courtesy of callum linehan.
here are two good articles from ‘radiographics’ on branchial cleft cysts.
thyroglossal duct cyst
ultrasound image – transverse thyroid. anterior to the right isthmus, a mobile, painless, superficial and palpable lump corresponds with a thyroglossal duct cyst.
ultrasound image – longitudinal. the cyst is well-circumscribed containing hypoechoic contents with posterior enhancement.
fna revealed milky fluid.
appearances vary and involve anechoic or hypoechoic fluid with thin walls. this may increase in echogenicity when infected.
power doppler image – no discernible internal vascularity. care must be taken if these appear to contain solid components due to the low incidence of papillary carcinoma.
images courtesy of callum linehan.
a myohyoid muscle abscess
ultrasound image- comparison of the myohyoid muscles. normal left, oedematous right,
ultrasound image- an abscess in the myohyoid muscle. longitudinal view.
ultrasound image- the increased vascularity in the wall of the abcsess is easily seen with power doppler.
laryngeal carcinoma
dual-screen ultrasound image of a hypoechoic laryngeal mass (scc) with irregular margins at the level of the epiglottis.
a curvilinear probe provided a larger depth and field of view to better define the relational anatomy – highlighted.
images courtesy of callum linehan.
ultrasound image – regional metastatic lymph nodes. these present with surrounding oedema – note the increased attenuation and echogenicity of the adjacent adipose tissue.
images courtesy of callum linehan.
ultrasound image – transverse to the larynx.
a large laryngeal scc presents as an ill-defined lobulated hypoechoic mass invading the thyroid cartilage and adjacent tissues.
images courtesy of callum linehan.
ultrasound image – longitudinal to the larynx. tumour extends beyond the thyroid cartilage into the adjacent thyroid tissue (highlighted anatomy).
images courtesy of callum linehan.
b-mode and colour doppler image. careful scanning provided clear windows to allow complete visualisation of the mass.
images courtesy of callum linehan.
b-mode and colour doppler image of a metastatic lymph node in a laryngeal scc case.
this case presented with a palpable neck lump for investigation seen above. questioning revealed dysphagia and dysphonia.
multiple metastatic lymph nodes were noted in the left c-chain. the exam was extended to the larynx which revealed the primary.
images courtesy of callum linehan.
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