Diagnostic ultrasound ( PDFDrive )

CHAPTER 19 The Thyroid Gland 707
A
B
C
D
FIG. 19.23 Malignant Follicular Neoplasms. (A) and (B) Longitudinal images of two patients with oval homogeneous hypoechoic masses.
(C) and (D) Transverse images of two other patients with round homogeneous masses. These four carcinomas appear identical to the benign
follicular neoplasms (see Fig. 19.13), and surgical removal is required to exclude or establish malignancy of most follicular tumors.
FIG. 19.24 Multicentric Medullary Thyroid Carcinoma. Transverse dual image in patient with multiple endocrine neoplasia type II (MEN II)
shows bilateral hypoechoic masses (arrows) that contain areas of coarse calciication. C, Carotid arteries; E, esophagus; Tr, trachea.
he sonographic appearance of medullary carcinoma is usually
similar to that of papillary carcinoma and is seen most oten as
a hypoechoic solid mass. Calciications are oten seen (histologically
caused by calciied nests of amyloid substance) and tend
to be more coarse than the calciications of typical papillary
carcinoma 34 (Fig. 19.25). Calciications can be seen not only in
the primary tumor but also in lymph node metastases and even
in hepatic metastases.
Anaplastic Thyroid Carcinoma. Anaplastic thyroid carcinoma
is typically a disease of elderly persons; it represents one
of the most lethal of solid tumors. Although it accounts for less
than 2% of all thyroid cancers, it carries the worst prognosis,
with a 5-year mortality rate of more than 95%. 35 he tumor
typically manifests as a rapidly enlarging mass extending beyond
the gland and invading adjacent structures. It is oten inoperable
at presentation. Anaplastic carcinomas are oten associated with
papillary or follicular carcinomas, presumably representing a
dediferentiation of the neoplasm. hey tend not to spread via
the lymphatics but instead are prone to aggressive local invasion
of muscles and vessels. 27
Sonographically, anaplastic thyroid carcinomas are usually
hypoechoic and oten encase or invade blood vessels and neck
muscles (Fig. 19.26). Oten these tumors cannot be adequately
examined by ultrasound because of their large size. Instead,