Diagnostic ultrasound ( PDFDrive )

1638 PART V Pediatric Sonography
A
B
FIG. 48.18 Submandibular Pleomorphic Adenoma. (A) Submandibular gland containing a well-deined hypoechoic mass. (B) Computed
tomography scan shows a well-deined low-density lesion centered within the right submandibular gland.
gland neoplasms, although ill-deined tumor margins and adjacent
lymphadenopathy are suspicious features. 52,53 For further deinition
of a lesion, MRI is the method of choice because it provides precise
information with regard to the nature of the mass as well as its
extent, especially the presence of perineural invasion. 15,24
Pleomorphic adenomas, also referred to as benign mixed-cell
tumors, contain both mesenchymal and epithelial cell lines. hese
neoplasms are the most common benign salivary gland tumor
in childhood and occur in all pediatric age groups (median, 15
years). 18,23 Most occur as a solitary, hard, painless, slow-growing
mass. 54 Approximately 60% to 90% of these lesions originate in
the parotid gland and 10% to 30% in the submandibular gland. 12,15
hese lesions can recur (1%-50%) as multiple masses or rarely
can develop late metastatic deposits. 54 On sonography, the lesion
appears lobulated, well deined, and hypoechoic or isoechoic
(with respect to normal salivary tissue) (Fig. 48.18). Cystic areas
and hyperechoic shadowing foci representing small calciications
may be noted. 11 Typically, pleomorphic adenomas demonstrate
peripheral vascularity with a hypovascular center. 13,24,29 Treatment
includes surgical resection with facial nerve sparing procedures
if in the parotid gland.
Warthin tumor, also referred to as papillary cystadenoma
lymphomatosum or adenolymphoma, is a rare benign salivary
gland neoplasm of children and solely identiied in the parotid
gland. 55,56 he lesion contains a double layer of epithelial cells
resting on a dense lymphoid stroma and is believed to result
from incorporation of lymphatic elements and heterotopic ductal
epithelium within the parotid lymph nodes. Ultrasound indings
include an oval, hypoechoic, well-deined mass containing multiple
microcystic or anechoic areas, given the high propensity for
cystic change. 12,13,55 With color and Doppler sonography, the
tumor typically is hypervascular. Technetium 99m scintigraphy
shows intense uptake in the tumor but is almost never performed
in children. 11,12 Treatment is surgical resection; however, recurrence
is possible from multifocality.
Mucoepidermoid carcinoma, the most common malignant
salivary gland neoplasm in children, consists of cords, sheets,
or cystic spaces lined by squamous and mucous cells. 11,15 Of the
malignant salivary gland lesions, 60% are diagnosed as mucoepidermoid
carcinomas, and about 50% arise from the parotid. 15
Clinically, these lesions may be tender, may grow rapidly, and
may cause facial nerve paralysis. 12 Most (76%) mucoepidermoid
carcinomas in children are of low grade. 57 Ultrasound characteristics
depend on histologic grade. However, increased intratumoral
RI and high peak systolic low velocity (>60 cm/sec)
should increase suspicion for malignancy. 29 Sonography should
also be performed in the area of the lesion to assess for metastaticappearing
lymph nodes. 58
Acinic cell carcinoma accounts for approximately 10% of
malignant salivary gland tumors, most commonly arising from
the parotid gland and less frequently from the submandibular
or minor salivary glands. 57 On ultrasound, these lesions are usually
irregular in shape with discrete margins, heterogeneous,
hypoechoic, and poorly vascularized 59 (Fig. 48.19). Lesions may
also demonstrate a mixed cystic and solid appearance and have
posterior acoustic enhancement. Importantly, these lesions may
be diicult to diferentiate from other benign masses. 59 Treatment
is usually wide surgical resection with radiotherapy reserved for
extraglandular extension, lymph node metastases, or local recurrences.
57 his tumor has the best prognosis of all malignant
salivary gland neoplasms. 60
Adenoid cystic carcinoma accounts for approximately 9%
of malignant salivary gland tumors in children, almost always
in the parotid gland. 57 hese are slow-growing tumors but have
increased association with perineural invasion. No speciic
sonographic characteristics are described. Pain and numbness
are present in 40% of children with adenoid cystic carcinoma
and strongly correlate with perineural invasion.
Sialoblastoma is a rare neonatal neoplasm of the salivary
gland, with less than 50 cases described in the literature. 61,62 his