Diagnostic ultrasound ( PDFDrive )

1648 PART V Pediatric Sonography
FIG. 48.35 Multinodular Goiter. Seventeen-year-old with thyroid
enlargement. Thyroid ultrasound image shows multiple nodules within
both lobes of the thyroid, some of which are small and hypoechoic and
others large and complex. See also Video 48.2.
characteristics, these lesions can be diicult to diferentiate from
malignancy. 87,112
Multinodular (adenomatous) goiter in children is uncommon
but typically is diagnosed in adolescent girls near puberty. 114 In
adults the etiology has been linked to iodine deiciency. In
children, genetic susceptibility is more common, although
autoimmune factors are also implicated. 115 Multinodular goiter
has been described in patients with renal cystic disease, polydactyly,
Hashimoto thyroiditis, McCune-Albright syndrome, and
previous radiation therapy. 114 At presentation, children are typically
euthyroid and clinically are diagnosed with a palpable nodule
or nodules. On ultrasound, the nodules show variable heterogeneity
with macronodular or micronodular formation (Fig. 48.35,
Video 48.2). Some may become cystic because of necrosis or
hemorrhage. 114 Continued ultrasound monitoring of these patients
is warranted given the increased risk for nonmedullary cancer. 115
hyroid cancer is rare in children and represents only 1.5%
of all malignancies in patients younger than 15 years. 90,106 However,
there is a 1.5- to 5-fold greater chance of a thyroid nodule being
malignant in children when compared with adults. 116,117 Among
girls 15 to 19 years of age, thyroid cancer is the second most
common malignancy. 118 Factors that are associated with increased
risk of thyroid cancer include a positive family history of thyroid
cancer, genetic predisposition, and radiation exposure, especially
in patients with history of bone marrow transplant. 87,119 Multiple
syndromes such as the PTEN hamartoma tumor syndromes
(which are caused by germline mutations of the PTEN tumor
suppressor gene), Cowden and Bannayan-Riley-Ruvalcaba
syndromes, familial adenomatous polyposis, Gardner syndrome,
Peutz-Jeghers syndrome, and Carney complex are associated
with thyroid nodules and cancers. 120 Autoimmune thyroiditis
has also been shown to be associated with a greater incidence
of thyroid cancers. 120,121 he irradiated thyroid can show a
spectrum of abnormalities, from cysts to benign or malignant
nodules. Incidence of thyroid cancer ater irradiation may increase
more than 20-fold, with a mean latency period of about 15 years. 109
Risk factors in the presence of radiation include female gender,
younger age at irradiation, and longer time since irradiation. 122
Patients with thyroid cancer usually have a palpable nodule or
cervical adenopathy and, rarely, hoarseness or pain. Papillary
cancer, the most common pediatric thyroid neoplasm, represents
80% of all cases and is multicentric in 20% of cases 121 (Fig. 48.36).
Metastatic disease with papillary tumor is through the lymphatics.
Follicular cancer represents 17% of thyroid cancers and metastasizes
through the bloodstream. Medullary cancers comprise
2% to 3% of thyroid cancers, secrete calcitonin, and are typically
diagnosed in patients with a strong family history or features of
multiple endocrine neoplasia type II (MEN IIa and IIb). At
presentation, children with medullary cancer are usually at an
advanced tumor stage, with lymph node involvement in 50% to
80% and metastasis to the lung in 6% to 18%. 90,109,123
Children with thyroid cancer have cervical and pulmonary
metastasis more frequently than adults. hey also have more
advanced disease and higher rate of recurrence. 116 Bone metastases
are, however, rare in children. With sonography, it can be diicult
to diferentiate benign from malignant thyroid masses. Helpful
diferentiating ultrasound criteria for malignancy include a
predominantly solid lesion, the presence of calciication (especially
microcalciications), hypoechogenicity, irregular margins, large
height-to-width ratio, absence of peripheral halo, intranodular
vascularity, and associated abnormal lymph nodes. 124-128 Unfortunately,
no size criteria are provided to distinguish benign from
malignant thyroid nodules. Needle biopsy or surgical resection
should be considered in children with suspicious sonographic
or clinical features, owing to the high increased risk (25%-50%)
of thyroid malignancy. 129 Follicular cancers oten mimic adenomas.
Adjacent lymph nodes should always be inspected, as the presence
of lymphadenopathy or calciication is concerning for metastatic
disease.
Malignant Thyroid Nodule: Sonographic
Characteristics
Predominantly solid lesion
Presence of calciication, especially microcalciications
Hypoechogenicity
Irregular margins
Large height-to-width ratio
Absence of peripheral halo
Intranodular vascularity
Associated abnormal lymph nodes
Nuclear medicine (frequently iodine-123 and iodine-131
scintigraphy) has been used to guide therapy because “cold”
nodules on scintigraphy are suspicious for malignancy. Although
“hot” nodules on nuclear medicine scintigraphy are usually not
malignant, exceptions can occur 103 (Fig. 48.37). In general, thyroid
neoplasms (excluding the medullary type) have a good prognosis,
with 10-year survival greater than 95% when treated with total
thyroidectomy, lymph node dissection, and postoperative iodine-
131 radioiodine therapy. 109
Other pediatric thyroid neoplasms include lymphoma and
teratoma. In pediatric patients with Hashimoto thyroiditis and
a solitary or multiple hypoechoic lesions, lymphoma should
considered. 90