Diagnostic ultrasound ( PDFDrive )

CHAPTER 48 The Pediatric Head and Neck 1639
A
B
FIG. 48.19 Parotid Acinic Cell Carcinoma. (A) Color Doppler shows a round hypoechoic mass arising from the left parotid gland. The mass
is hypovascular, but there is peripheral increased vascularity on color Doppler. (B) The mass in the left parotid gland is moderately enhancing and
dificult to separate from the parotid gland (arrow).
lesion consists of basaloid and myoepithelial cells that are reminiscent
of the developing salivary anlage. 61 he lesion is most
frequent in the parotid gland and less common in the submandibular
gland. his lesion oten manifests as a large parotid mass
identiied in early infancy or childhood, although prenatal and
some adult cases have also been described. Sialoblastoma is a
focally aggressive tumor, with local recurrences and infrequent
distant metastases. 62 Sonographic characteristics are not well
described. However, descriptions include that of a multinodular
well-deined predominantly hypoechoic salivary gland mass with
multiple septations and without increased vascularity. 63,64 On
MRI, heterogeneous appearance is oten described, with areas
of hemorrhage or necrosis. 61,65,66 here are few case reports of
combined sialoblastoma and hepatoblastoma. 63,67,68
Other Salivary Gland Lesions. Lingual thyroid may appear
as a homogeneous solid mass in the midline dorsum of the tongue.
In 70% of patients, this ectopic tissue is the only functioning
thyroid tissue.
Rhabdomyosarcoma occurs 40% of the time in the head and
neck and can arise from any muscle. his is the second most
common malignancy in the parotid and submandibular spaces
in the pediatric population. 50 Salivary gland involvement is
frequently by direct extension. 69
Primary lymphoma of the salivary glands is termed
MALToma, denoting origin from mucosa-associated lymphoid
tissue. Patients with Sjögren syndrome and other autoimmune
disease, including HIV, are at risk for primary lymphoma. Secondary
involvement of lymphoma is rare, but more common in
the parotid. 70 Ultrasound demonstrates a focal mass or difuse
iniltration with an enlarged gland. Lesions may consist of multiple
small, hypoechoic nodules or an irregularly shaped, heterogeneous
mass without calciication or cystic degeneration. 70 A reported
case of submandibular gland involvement by MALToma showed
hypoechoic compartments surrounded by hyperechoic lines,
creating a tortoiseshell appearance. 71 Increased color Doppler low
is typical.
Lipomas represent 1% of parotid tumors; 57% of lipomas
in the parotid area arise within the gland. hese lesions are
compressible, oval, and well deined. On ultrasound, lipomas
contain striped or feathered internal echoes devoid of color and
Doppler low. 23 In younger children, lipoblastomas are more
common. 72
Leukemic iniltration is rare, with a presentation similar to
lymphoma on ultrasound. 73
Metastatic disease is rare in children but would include
neuroblastoma and thyroid cancer. 43,74
Peripheral nerve sheath tumors including neuroibroma
and schwannoma can occur in the parotid gland, oten in
relation to the facial nerve. 75,76 Multiple or plexiform neuroibromas
are typical in patients with neuroibromatosis type 1. 69
Sonography demonstrates multiple hypoechoic areas within
the gland. 77
Suprahyoid Cystic Lesions
In the parotid space, type I branchial cysts are most common.
Simple cysts of the salivary glands are rare and likely caused by
mucous retention. On ultrasound, the lesions are well deined
and anechoic, with posterior acoustic enhancement and no
internal blood low. 12,74 In the preauricular region, supericial
to the parotid gland, dermoid and epidermoid cysts may
also occur.
In the submandibular space laterally, type II branchial cysts
can be identiied posterior to the submandibular gland. Lymphatic
malformations may also extend into the space. Ranulae (sublingual
cysts) are mucous retention cysts resulting from obstruction
of the sublingual gland or duct. hey present paramidline,
in the area of the sublingual gland, as a painless swelling along
the loor of the mouth. When large, sublingual cysts can extend