Diagnostic ultrasound ( PDFDrive )

712 PART III Small Parts, Carotid Artery, and Peripheral Vessel Sonography
TABLE 19.2 Reliability of Sonographic
Features in Differentiation of Benign From
Malignant Thyroid Nodules
PATHOLOGIC
DIAGNOSIS
Feature Benign Malignant
SHAPE
Wider than tall +++ ++
Taller than wide + ++++
FIG. 19.30 Fine-Needle Aspiration of Thyroid Nodule Caused by
Follicular Neoplasm. Transverse image shows a large nodule replacing
the right thyroid lobe. Tr, Tracheal air shadow. The tip of the 25-gauge
needle is highly visible (arrow), and the shaft of the needle is faintly
visible.
Ater partial or near-total thyroidectomy for carcinoma,
sonography is the preferred method for follow-up, by detecting
residual, recurrent, or metastatic disease in the neck. 57 In
patients who have had subtotal thyroidectomy, the sonographic
appearance of the remaining thyroid tissue may serve as an
important factor in deciding whether complete thyroidectomy
is recommended. If a mass is identiied, its nature can be determined
by ultrasound-guided FNA (Fig. 19.30). If no masses are
seen, the clinician may choose to follow the patient with periodic
sonographic studies. For patients who have had total or near-total
thyroidectomy, sonography has proved to be more sensitive than
physical examination in detecting recurrent disease within the
thyroid bed or metastatic disease in cervical lymph nodes. 58
Patients with a history of thyroid cancer oten undergo periodic
sonographic examinations of the neck to detect nonpalpable
recurrent or metastatic disease. When a mass is identiied, FNA
under sonographic guidance can establish a diagnosis of malignancy
and help in surgical planning.
Differentiation of Benign and Malignant Nodules
According to several reports, for the diferentiation of benign
from malignant thyroid nodules, sonography has sensitivity rates
of 63% to 94%, speciicity of 61% to 95%, and overall accuracy
of 78% to 94%. 4,5,59-65 Currently, no single sonographic criterion
distinguishes benign thyroid nodules from malignant nodules
with complete reliability. 5,59-61,65 Nevertheless, certain sonographic
features are seen more oten with one type of histology
or another type, thus establishing general diagnostic trends 31
(Table 19.2).
he fundamental anatomic features of a thyroid nodule on
high-resolution sonography are as follows:
• Internal consistency (solid, mixed solid and cystic, or purely
cystic)
• Echogenicity relative to adjacent thyroid parenchyma
• Margin
• Shape
• Presence and pattern of calciication
INTERNAL CONTENTS
Purely cystic content ++++ +
Cystic with thin septa ++++ +
Mixed solid and cystic +++ ++
Comet-tail artifact +++ +
ECHOGENICITY
Hyperechoic ++++ +
Isoechoic +++ ++
Hypoechoic +++ +++
Markedly hypoechoic + ++++
HALO
Thin halo ++++ ++
Thick, incomplete halo + +++
Absent + +++
MARGIN
Well deined +++ ++
Poorly deined ++ +++
Spiculated + ++++
CALCIFICATION
Eggshell calciication +++ ++
Coarse calciication +++ +
Microcalciication ++ ++++
DOPPLER
Peripheral low pattern +++ ++
Internal low pattern ++ +++
SONOELASTOGRAPHY
Patterns 1 and 2 ++++ +
Patterns 3 and 4 + +++
+, Rare (<1%); ++, low probability (<15%); +++, intermediate
probability (16%-84%); ++++, high probability (>85%).
Data from authors’ experience and literature reports.
• Peripheral sonolucent halo
• Presence and distribution of blood low signals
Internal Contents. In our experience, approximately 70%
of thyroid nodules are solid, whereas the remaining 30% exhibit
various amounts of cystic change. A nodule that has a signiicant
cystic component is usually a benign adenomatous (colloid)
nodule that has undergone degeneration or hemorrhage. When
detected by older, lower-resolution ultrasound machines, these
lesions were called “cysts” because the presence of internal debris
and a thick wall could not be appreciated. Pathologically, a true