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Thyroid Gland

Tumor

Malignant tumors are difficult to diagnose. Large tumors tend to develop areas of ne-

crotic liquefaction. Together with calcifications, they produce a complex echo pattern with an irregular sonomorphologic structure that is difficult to interpret (Figs. 14.62, 14.63, 14.64). The diagnosis relies chiefly on radionuclide findings (cold nodules), clinical manifestations (enlarging goiter), and FNA biopsy.

Fig. 14.62 Follicular carcinoma within a goiter. Fine-needle biopsy (FNB) in the ventral lateral areas: follicular neoplasia. Histology: follicular carcinoma.

a Intensive complex structure.

b Marked vascularization.

Fig. 14.63 Papillary thyroid carcinoma of the right thyroid lobe: diffuse hypoechoic structure, small shadows (image courtesy of Dr. H. Strobel, University of Erlangen, Germany).

f Fig. 14.64 Undifferentiated anaplastic carcinoma shows an irregular structure with a hypoechoic background, internal vascularity, central anechoic foci of liquefaction, and echogenic microcalcifications.

14.4 s–u). Definitive treatment for hyperthyroidism should be withheld in these cases, and replacement therapy should be instituted despite the hyperthyroidism.

Given the important role of ultrasonography in patients who present with hyperthyroid symptoms, the causes of hyperthyroidism are listed in 14.4 and illustrated with ultrasound images and correlative radionuclide scans. The examples do not include hyperthyrosis factitia (hyperthyroidism induced by the exogenous administration of thyroid hormones) or hyperthyroidism as a paraneoplastic syndrome.

14

Differential Diagnosis of Hyperthyroidism

Multifocal autonomy

Disseminated autonomy

f Predominantly left-sided goiter with bifocal autonomy.

i Multifocal autonomy.

l Disseminated autonomy with confirmed hyperthyroidism.

14

Thyroid Gland

14.4 Hyperthyroidism: Ultrasound Findings and Correlative Scintiscans (Continued)

Disseminated autonomy in AIT (PAS type II)

Graves disease with focal autonomy (Marine–Lenhart syndrome)

p Graves disease: marked hypoechoicity and swelling of the left lobe, also nodules (one marked with an arrow). AC = carotid artery.

q Hypervascularity in one of the nodules, which here appears more reflective than the otherwise hypoechoic thyroid gland. AC = carotid artery.

r Graves thyroid shows increased radiotracer uptake predominantly in the left lobe.

s Hypoechoic thyroid gland (TH) with a circumscribed, anechoic bandlike area on the right side; incipient thyrotoxicosis. Anti-TPO > 1000, anti-TSH receptor antibodies slightly elevated.

t Pronounced hypervascularity in the patchy echo-free lesion in s. The vesselspared area is a cyst (C). The rest of the thyroid also shows increased vascularity.

u Scintiscan shows intense uptake in the right lobe and decreased uptake in the left lobe.

●Thyroid gland ultrasonography with high-res- olution probes may yield the appearance of an “inhomogeneous” structure with fine cystic lesions like small vessels or lymph cysts although this is actually a normal finding.

●Small adenomas (< 1 cm) are not visible in radioiodine thyroid scan, therefore this method should not be used; follow-ups with ultrasound are recommended when no hyperthyroidism is present.

●Volume estimation should be done in every thyroid examination; it appears to be accurate enough to be useful and the isthmus is not

measured. The depth may be measured in transverse scan direction in the deepest diameter. Measuring procedures are difficult in large goiters because of the limited probe diameter (4–5 cm), in which case convex probes can be used; alternatively, divided images may be helpful (Fig. 14.65). A volume of over 50 mL results in a less accurate measurement.

●Ultrasonography can demonstrate an impression of the trachea in case of stridor.

Fig. 14.65 Nodular goiter, atypical longitudinal scan left lobe; compound double image: the left thyroid lobe exceeds the image limits, so the length has to be estimated (volume of the left lobe 45 mL, of the whole thyroid ca. 88 mL).

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Differential Diagnosis of Hyperthyroidism