Author: Katya Shpilberg
Grayscale Ultrasound Doppler CT MRI - T1 MRI - T2 MRI - postcontrast T1 Gross Pathology Histology Additional comments or images
Benign neoplasms:
Pleomorphic adenoma hypoechoic, well-defined, lobulated w/ posterior acoustic enhancement; +/- calcs

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peripheral vascularity w/ hypovascular center typical variable enhancement typically gradually progressive & avid; +/- calcifications

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Image 2 (delayed)
uniformly hypointense when small, low to intermediate signal when large; may have a capsule

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uniformly hyperintense when small, intermediate to high signal when large; may have a capsule

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Image 3: ADC (high ADC value helps differentiate from malignant neoplasms)
variable enhancement typically gradually progressive & avid; infiltration into parapharyngeal space, muscles & bone may indicate capsule rupture or malignant transformation

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Patient 2: early

Patient 2: delayed
soft tan lobules representing epilial component interspersed among lobulated firm, white, gritty chondromyxoid component; fibrous capsule. admixture of epilial & chondromyxoid elements MC benign parotid neoplasm; middle-aged women; unilateral & solitary; superficial lobe; lobulated shape/ bosselated contour; post-op seeding may occur; may undergo malignant transformation after decades.
Warthin tumor (cystadenoma lymphomatosum) oval, hypoechoic, well-defined; +/- multiple anechoic areas; may appear as simple cyst

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often hypervascularized but may contain only short vessel segments strong, uniform enhancement; +/- central cystic or necrotic areas +/- washout Image 1: hypointense, well-circumscribed, homogeneous, cystic or solid

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Image 1: well-circumscribed; variable signal but typically hyperintense (atypical image shows hypointense)

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typically uniform enhancement; peaks early +/- washout; can have central non-enhancing cystic area.

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encapsulated, soft, ovoid w/ smooth, lobulated surface; tan tissue w/ cystic spaces that contain mucoid, brown or thin, yellow fluid double layer of oncocytes (epithilial cells) resting on a dense lymphoid stroma incr upt on T99m pertechnetate, FDG-PET, & thallium-201 chloride scans

2nd MC benign neoplasm in adults; elderly men; b/l in up to 10%; often multiple; parotid tail; associated w/tobacco; no malignant potential
Infantile hemangioma (capillary hemangioma) discrete intraparotid masses or diffuse infiltration; enlarged gland w/altered echogenicity. variable increase in flow; can be very hypervascular well-defined mass w/ uniform, intense enhancement; may contain phleboliths. typically low to intermediate signal w/ flow voids typically hyperintense w/ flow voids intense enhancement including of flow voids lobules of capillaries w/ evidence of cellular proliferation clusters of plump endothelial cells, pericytes & mast cells; frequent mitotic figures; multi-laminated endolial basement membrane MC benign pediatric salivary gland mass; enlarges in 1st yr of life; F > M; may spontaneously regress.

Angiography: hypervasc mass w/ dense, prolonged capillary blush; enlarged feeding & draining vessels; no true AV shunting
Lipoma oval & hypoechoic w/ sharp margins; compressible; hyperechoic linear structures regularly distributed in striated or feathered pattern only single vessel segments may be found well-defined mass of uniform fat-density; no enhancement; significant enhancement should raise concern of liposarcoma. markedly hyperintense; signal suppression on fat-saturated MR sequences mildly hyperintense; signal suppression on fat-saturated MR sequences no enhancement; significant enhancement should raise concern of liposarcoma encapsulated, smooth or lobulated, soft yellow masses mature adipocytes that are uniform in size & shape; occasional fibrous connective tissue septations
Neurofibroma ovoid, well-demarcated, homogeneous; +/- multiple small cystic areas; lobulated & infiltrating if plexiform ovoid, well-demarcated, homogeneous; isodense; +/- multiple small cystic areas; moderate enhancement; marked enhancement if plexiform. low to intermediate signal intensity; +/- heterogenous areas of different signal intensities high signal intensity; +/- heterogenous areas of different signal intensities moderate enhancement; marked enhancement if plexiform loose connective tissue fibers randomly distributed among tapering nerve fibers may arise from  intraparotid facial nerve trunk in NF1; difficult to distinguish from pleomorphic adenomas outside  clinical context
Angiolipoma Image 1: Noncontrast. Circumscribed mass w/ fat & soft tissue density components

Image 2: Contrast-enhanced. marked enhancement around  fatty components
heterogenous w/ markedly hyperintense components due to fat heterogenous marked enhancement around  fatty components difficult to differentiate from hemangioma w/ fatty degeneration; infiltrating form is less common
Oncocytoma small, well defined small, well defined small, well defined, hypointense to normal parotid gland isointense to hyperintense to normal parotid gland same enhancement as  normal parotid gland mitochondria-rich oncocytes rare benign tumor; associated w/ prior radiation; mimics lymph node on imaging.

increased radiotracer uptake at technetium pertechnetate scan.
Schwannoma well-defined oval mass in superficial lobe; often contains anechoic areas well-defined oval mass in superficial lobe; enhances. well-defined oval mass in superficial lobe target appearance w/ peripheral lower T2 signal enhances originates from facial nerve; target-appearance on T2 is highly suggestive
Malignant neoplasms:
Features characteristic of all malignancies high vascularization, high systolic peak flow velocity and/or increased intratumoral vascular resistance index may indicate malignancy but are non-specific Ill defined margins suggest higher grade Ill defined margins suggest higher grade. T2: lower T2 signal is a reasonably reliable predictor of malignancy

ADC. Malignancies may demonstrate diffusion restriction/lower ADC signal than benign neoplasms
deep infiltration into parapharyngeal space, muscles & bone strongly suggest malignancy; Best study to determine perineural spread Imaging findings of parotid malignancies are largely nonspecific and true diagnosis typically requires tissue sampling
       
Mucoepidermoid carcinoma smooth margins & large cystic areas when low-grade, more solid than cystic areas when high-grade See typical malignancy features above smooth margins when low-grade; +/- calcs; no significant enhancement when low grade, more solid homogeneously enhancing areas w/ increasing grade.

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smooth margins when low-grade; hypo- to isointense hyperintense w/ smooth margins when low grade; intensity decreases w/ higher grade

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no significant enhancement when low-grade; more solid homogeneously enhancing areas w/ increasing grade. gray, tan-yellow, or pink squamous & mucous cells arranged in cords, sheets, or cystic configurations (image of high grade) most common malignant salivary gland neoplasm in children; most common parotid malignancy in adults; may show several levels of differentiation; low grade resembles pleomorphic adenoma & high grade Warthin's tumor on imaging so aspiration/biopsy is needed; prognosis depends on tumor grade
Adenoid cystic carcinoma See typical malignancy features above typically enhance low to intermediate signal intensity moderate signal intensity; high grade tend to be lower in signal intensity solid enhancement; tendency for perineural spread (on CN 7 +/- CN 5) manifested as enhancement (image w/ perineural spread) pink or tan w/ mottled surface; rarely necrotic change; infiltrative margins; no capsule Three distinct histological patterns: cribriform, tubular & solid; tumor may have one, two or three of these 2nd MC parotid malignant neoplasm in adults; slow growing; late metastases; favorable prognosis
Malignant mixed tumor (carcinoma ex-pleomorphic adenoma) See typical malignancy features above Typically enhance.
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Coronal
typically hypointense typically low to intermediate signal intensity typically enhance result from malignant transformation of long-standing pleomorphic adenoma; poor prognosis
Acinic cell carcinoma may be well-defined w/ regular margins; can be associated w/ mandibular destruction See typical malignancy features above typically enhance typically hypointense; can be well-defined typically low to intermediate signal intensity; can be hyperintense. Image 1: early enhancement

Image 2 (delay): washout typical
may present as multiple painless masses; favorable prognosis
Adenocarcinoma often associated w/ locoregional lymphadenopathy See typical malignancy features above typically enhance typically hypointense typically low to intermediate signal intensity typically enhance poor prognosis
Squamous cell carcinoma See typical malignancy features above typically enhance typically hypointense almost always hypointense typically enhance can arise de novo or from extranodal spread; poor prognosis
Undifferentiated (ductal) carcinoma See typical malignancy features above typically enhance typically hypointense typically low to intermediate signal intensity typically enhance no specific imaging features; very poor prognosis
Metastases metastatic lymph nodes may be well-defined & oval/ round; inhomogeneous echotexture w/ loss of fatty hila suggest metastatic disease (image of adenoca) typically increased vascularity (Image of metastatic melanoma) Image 1 (axial): variable appearance depending on primary neoplasm

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variable appearance depending on primary neoplasm (image of melanoma mets) variable appearance depending on primary neoplasm (image of melanoma mets) variable appearance depending on primary neoplasm (image of melanoma mets) adenopathy more common than direct mets; usually paraglandular in location; typically from locoregional spread from scalp, external auditory canal or cheek skin squamous cell carcinoma or melanoma; systemic mets rarely involve parotid but can result from melanoma, breast ca, lung ca & rarely RCC
Lymphoma discrete hypoechoic mass; may be multiple; may present as diffuse infiltration characterized by an enlarged gland w/ altered echogenicity demonstrate increased flow mild to moderate homogeneous enhancement; central necrosis may be present; focal masses confined to intraparotid lymph nodes or diffuse parotid infiltration. homogeneous intermediate signal intensity homogeneous intermediate signal intensity; more conspicuous on STIR; central hyperintensity if necrosis is present mild to moderate homogeneous enhancement, central necrosis may be present well-circumscribed, encapsulated, soft, fleshy masses sheets of lymphoid cells arranged in diffuse or follicular pattern; furr subdivided into small cleaved & large cell variants foci of increased activity on FDG-PET & 67-Gallium scans (image of PET-CT)

MALToma when primary; secondary salivary gland involvement by lymphoma is MC in parotids; NHL >> Hodgkin's
Rhabdomyosarcoma cannot define  full extent of  mass variable enhancement; indistinct margins; isodense to muscle; heterogenous; bony erosion. isointense; high signal foci due to hemorrhage in ~30% heterogenously hyperintense enhances diffusely; infiltrating appearance w/ indistinct margins pink-gray mass w/ frequent areas of hemorrhage & necrosis; may be grape-like (sarcoma botryoides) undifferentiated “blue cells” w/ scant cytoplasm & primitive-appearing nuclei most common pediatric soft tissue sarcoma; parotid involved by direct extension; perineural spread is common; FDG-avidity on PET has been observed.
Leukemia diffuse enlargement w/ altered, variable echogenicity increased blood flow variable attenuation & enhancement variable signal intensity variable signal intensity variable enhancement indistinguishable from or causes of parotid gland enlargement, including infiltrative lymphoma
Infectious/Inflammatory lesions:
Parotitis enlarged & inhomogeneous gland w/ multiple small, oval, hypoechoic areas increased blood flow diffuse enhancement w/ low-attenuating foci slightly hypointense slightly hyperintense may demonstrate marked enhancement most common parotid disease in children; usually viral (mumps); can result from obstructing sialolithiasis
Abscess hypoechoic or anechoic w/ posterior acoustic enhancement & unclear borders; +/- echogenic rim; +/- moving debris and/or hyperechoic foci of gas peripheral enhancement, often irregular; low-attenuation collection. hypointense, particularly in its central aspect hyperintense, particularly in its central aspect peripheral enhancement, often irregular restricted diffusion is typical, particularly in its center; usually bacterial.
Benign-lymphoepilial lesions- HIV numerous small, hypoechoic or anechoic lesions throughout  enlarged gland no internal enhancement of small cystic lesions; bilateral gland enlargement w/ intraglandular small cystic masses; some masses maybe hyperdense due to protein/ hemorrhage. bilateral gland enlargement w/ intraglandular small hypointense cysts; hyperintense proteinaceous/ hemorrhagic cysts may occur bilateral gland enlargement w/ intraglandular small hyperintense cysts no internal enhancement of small cystic lesions intranodal cyst lined w/ epilial cells characteristic HIV lesions; associated w/ cervical lymphadenopathy & enlarged adenoids; may present as multiple painless masses
Tuberculosis focal, intraparotid, nearly anechoic zones that might have a cavity or cavities no color flow in necrotic caseous cavities gland enlargement w/ calcification; may contain hypodense areas; often b/l; +/- peripheral enhancement reflecting an abscess. can have peripheral enhancement reflecting an abscess parotid is  most commonly involved salivary gland w/ TB; typically results from extension of cervical adenopathy
Sjogren syndrome inhomogeneous echotexture w/ scattered multiple, usually well-defined, small, oval, hypoechoic or anechoic areas increased parenchymal blood flow heterogenous enhancement of enlarged gland; ranges from normal appearance to glandular enlargement w/ variable attenuation; hypointense areas indicate cystic changes & fat deposition; atrophic gland in late stages enlarged heterogenous-appearing gland; “salt & pepper” or “honeycomb” appearance when advanced enlarged glands containing multiple hyperintense cysts; duct destruction best seen on heavily T2-weighted MR sialogram

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Image 2: MR Sialogram
heterogenous enhancement of enlarged gland lymphocytic infiltrate is seen in association w/ destruction of parotid gland tissue;; Title: From Education Exhibit "Swelling at  Angle of  Mandible: Imaging of  Pediatric Parotid gland & Periparotid Region intraglandular contrast pooling can be seen on conventional sialogram

Increased risk of salivary gland lymphoma (typically aggressive)
Sarcoid single or multiple hypoechoic areas in an enlarged or normally sized gland; may be manifested as diffuse low echogenicity blood flow may be increased multiple benign-appearing, non-cavitating masses; often bilateral; may contain calcifications; gland may be enlarged

heterogenous enhancement of gland; gland may be enlarged
multiple benign-appearing, non-cavitating masses; often bilateral; gland may be enlarged multiple hyperintense benign-appearing, non-cavitating masses; often bilateral; gland may be enlarged heterogenous enhancement of gland; gland may be enlarged confluent, non-necrotizing epilioid granulomas increased uptake on Gallium-67 scan

parotid gland involved in ~30%
Langerhans cell histiocytosis diffuse enlargement & hypoechogenicity of gland hyperenhancement of enlarged glands; bilateral homogenous gland enlargement; no necrosis or calcification. bilateral homogenous gland enlargement bilateral homogenous gland enlargement hyperenhancement of enlarged glands pediatric population; can be  first manifestation of disease
Amyloidosis can cause diffuse gland enlargement can cause diffuse gland enlargement can cause diffuse gland enlargement can cause diffuse gland enlargement very rare
Congenital/ miscellaneous lesions:
Lymphangioma (lymphatic malformation) multicystic w/ thin septations; solid elements may be present typically no flow or than in septations multi-lobulated w/ septations & cystic areas; may contain fluid-fluid levels; typically does not enhance; solid elements may enhance. Image 1: multilobulated, predominantly hypointense; multiple fluid-fluid interfaces w/ variable signal intensity due to hemorrhage of different age

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multilobulated, predominantly hyperintense; multiple fluid-fluid interfaces w/ variable signal intensity due to hemorrhage of different age

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Image 1: typically does not enhance; solid elements may enhance.

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smooth, gray, glistening, non-encapsulated mass dilated endolial-lined lymphatic spaces; internal septations w/ varying thickness; may have dilated, thin-walled vessels w/in mass  65% present at birth, 90% detected by age 2; can be trans-spatial; may be complicated by infection or hemorrhage
Venous malformation multilobulated; loculations w/ possible fluid levels; compressible; hyperechoic shadowing structures reflect phleboliths venous flow may be observed & augmented by compression w/ transducer multilobulated; loculations w/ possible fluid levels; +/- phleboliths; +/-remodeling of adjacent bone & fat hypertrophy; variable enhancement, may be delayed; enlarged draining veins may be seen. multilobulated; loculations w/ possible fluid levels; hypertrophy of adjacent fat lesions w/ large vascular channels appear cyst-like, hyperintense, septated; lesions w/ smaller vascular channels appear more solid & intermediate in signal intensity (image of T2*/GRE) enhancement is variable in intensity & homogeneity; enlarged draining veins may be visualized; may have delayed enhancement. poorly circumscribed conglomeration of venous channels venous channels that vary in luminal diameter & wall thickness; lined by flat, mitotically inactive endolium & scant mural smooth muscle; absent internal elastic lamina; luminal thrombi; phleboliths phleboliths may be seen on plain films; often trans-spatial.
First branchial cleft cyst typically anechoic; may contain internal echoes due to hemorrhage/ protein demonstrates no flow no internal enhancement; slight enhancement of  capsule hypointense w/ possible regions of increased signal due to hemorrhage/ protein hyperintense no internal enhancement; slight enhancement of  capsule usually contains thick mucous thin outer layer of fibrous tissue forms a pseudocapsule; inner layer of flat squamoid epilium; germinal centers & lymphocytes may be present in cyst wall type 1: preauricular or intraparotid, +/- sinus tract to middle ear or medial EAC

type 2: posterior or inferior to angle of mandible, +/- sinus tract to lateral EAC
Cyst anechoic w/ posterior acoustiic enhancement, imperceptible wall & well-defined margins avascular fluid attenuation, or uniformly hyperdense due to protein/ hemorrhage; no internal enhancement; +/- faint peripheral enhancement hypointense; may be hyperintense due to protein/ hemorrhage Hyperintense no internal enhancement; may demonstrate faint enhancement along  periphery uncommon; can be congenital or acquired; pseudocysts w/ fibrous lining may also occur
Sialolithiasis echogenic; can have posterior acoustic shadowing

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Image 1: very hyperdense since typically calcified

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markedly hypointense; detection facilitated by use of heavily T2-weighted MR- sialogram frequently can be seen on plain films (image of conventional sialogram). ~4 times less common than in submandibular gland; increased incidence w/ strictures; produces dilatationof Stenson duct if obstructive; may result in inflammatory changes & cause parotitis.
Sialocele anechoic; can contain echogenic debris avascular typically hypodense unless contains hemorrhagic/ proteinaceous products; does not enhance. typically hypointense unless contains hyperintense hemorrhagic/ proteinaceous material. hyperintense; heavily T2-weighted MR-sialogram deminstrates communication w/ parotid duct does not enhance opacifies on conventional sialogram since communicates w/ parotid duct. usually post-traumatic, particularly penentrating trauma.
Sialosis bilateral gland enlargement bilateral gland enlargement; slightly greater than normal density bilateral gland enlargement bilateral gland enlargement; slightly higher than normal signal painless, usually symmetric; caused by DM, hypothyroidism, alcoholism, obesity, starvation & some medications (phenothiazines & several diuretics); may resolve if underlying cause resolves