Diagnostic ultrasound ( PDFDrive )

CHAPTER 19 The Thyroid Gland 697
A
B
C
D
FIG. 19.10 Colloid Cysts. Transverse (A) and longitudinal (B)-(D) images of four patients show the typical appearance of colloid cysts. Some
of the nodules have tiny echogenic foci that are thought to be microcrystals. A few of these foci are associated with comet-tail artifacts (arrow in
[A]) posteriorly. Nodules that are mostly cystic, such as these, are considered benign. Colloid cysts often contain internal echoes.
of colloid hyperplastic nodules from the vegetations seen in
papillary carcinomas; before moving to aspiration cytology studies,
contrast-enhanced sonography with second-generation microbubbles
and nondisruptive imaging can be used. Benign septa
and intracystic contents do not show enhancement (and “disappear”
in harmonic mode) (Fig. 19.12), whereas malignant
vegetations show intense enhancement in arterial phase with
relatively fast wash-out.
Adenoma
Adenomas represent only 5% to 10% of all nodular disease of
the thyroid and are seven times more common in women than
men. 5 Most result in no thyroid dysfunction; a minority (<10%)
hyperfunction, develop autonomy, and may cause thyrotoxicosis.
Most adenomas are solitary, but they may also develop as part
of a multinodular process.
he benign follicular adenoma is a true thyroid neoplasm,
characterized by compression of adjacent tissues and ibrous
encapsulation. Various subtypes of follicular adenoma include
the fetal adenoma, Hürthle cell adenoma, and embryonal
adenoma, each distinguished according to the type of cell
proliferation. he cytologic features of follicular adenomas are
generally indistinguishable from those of follicular carcinoma.
Vascular and capsular invasion are the hallmarks of follicular
carcinoma, identiied by histologic rather than cytologic analysis.
Needle biopsy is therefore not a reliable method to distinguish
between follicular carcinoma and cellular adenoma. herefore
such tumors are usually surgically removed.
Sonographically, adenomas are usually solid masses that may
be hyperechoic, isoechoic, or hypoechoic (Fig. 19.13, Video 19.3).
hey oten have a thick, smooth peripheral hypoechoic halo
resulting from the ibrous capsule and blood vessels, which can
be readily seen by color Doppler imaging. Oten, vessels pass
from the periphery to the central regions of the nodule, sometimes
creating a “spoke and wheel” appearance. his vascular pattern
is usually seen in both hyperfunctioning and poorly functioning
adenomas and thus does not allow the detection of hyperfunctioning
lesions.