Radiological imaging of salivary gland diseases.

Dr/ ABD ALLAH NAZEER. MD.

Imaging modalities available to assess salivary glands include:Plain film radiography.Sialography.CT scan.MRI.Diagnostic ultrasound.Nuclear scintigraphy.These imaging modalities play an important role in evaluating a patient with pain, swelling, or other symptoms related to possible salivary gland disorders. Imaging helps in differentiating lesions of salivary glands from those of parapharyngeal space, masticator space, and mandible, submandibular and submental spaces. In addition to localizing the lesion, it also aids in determining the extent of disease, involvement of skull base, mandible, and neural spread in case of malignant lesions.

Plain film radiographs: were used to determine salivary gland abnormalities before the development of more sophisticated imaging techniques. It is the least sensitive of all the imaging modalities. It is least expensive and readily available. It will readily demonstrate calculi. It also helps in differentiating bony / cartilaginous lesions that may mimic salivary gland pathology. Salivary glands should be imaged in multiple planes. Attempt should be made to isolate calcification / overlying calculi from bony mandible. Plain film imaging is useful in evaluating calculi, detecting calcification in hemangiomas, and evaluation of lymph nodes.Plain film imaging of parotid region should be performed with the patient positioned with extended chin, open mouth posterioanterior view with cheek blown out. This method will help in imaging stenson’s duct. In viewing submandibular region an extended chin, open mouthed lateral view is obtained. The patient is instructed to depress the tongue with his finger.Sialography: It was first performed by Arcelin in 1913. He used bismuth as the contrast media. He demonstrated submandibular gland calculus using this imaging technique. Before the advent of modern imaging modalities, Sialography was the mainstay in diagnosing inflammatory and neoplastic lesions of salivary glands. Because of their greater sensitivity.

CT scan: This has revolutionized salivary gland imaging. It provides precise anatomical detail and is routinely used as a primary imaging modality in salivary gland lesions. It is very useful in evaluating salivary gland calculi and associated adnexal inflammation. It is inferior to Sialography in studying the ductal system. Parotid gland CT density is highly variable. It tends to be intermediate between fat and muscle. The submandibular glands have less fat than the parotids. Their density is closer to that of muscle. CT of parotid gland is obtained by using thin section slices in axial and rarely coronal images. This is usually performed after intravenous injection of contrast solution. Mild enhancement of parotid gland takes place after contrast injection. Images are usually filmed with conventional soft tissue windows. Bone windows are useful for evaluating calcification, calculi formation, or adjacent bone involvement.MRI: Usually is complementary to CT because of its excellent soft tissue delineation capability. It is better than CT in differentiating parotid from extra parotid masses.

CT / MRI have replaced Sialography in the evaluation of salivary gland. Sialography will give some indication about whether a mass is intrinsic / extrinsic to the gland. Digital subtraction Sialography is still a favoured imaging modality in detection of sialolithiasis within Stensen and Wharton’s ducts.Sialography is contraindicated in cases of acute infections of salivary glands.

It fails to demonstrate the parotid gland in its entirety because of intervening mandible. It also does not clearly demonstrate the intraglandular facial nerve branches. Color Doppler studies of salivary glands indirectly identifies malignant lesions of salivary glands as these lesions boast high vascularity in comparison with their benign counterparts.Radionuclide imaging: Is rarely used to evaluate salivary glands. Sodium pertechnetate (technetium 99m) is the commonly used element. This isotope is concentrated and excreted by salivary glands. Since most salivary gland tumors do not accumulate the radionuclide, a tumor mass will appear as a filling defect on this scan. Tumors like warthin’s readily take up pertechnetate resulting in formation of “Hot spots”. Gallium 67 citrate is useful for studying inflammatory / neoplastic disease of salivary glands and adjacent areas. Since Gallium 67 is actively taken up by actively dividing cells, excessive gallium accumulation is seen in inflammatory and neoplastic processes like sarcoidosis / lymphoma etc.

Ultrasonography: High resolution Ultrasonography (7.5 – 10 MHz) of parotid and submandibular salivary glands is actually a quick and non invasive method for assessing these glands. It helps in the assessment of vascularity of the gland, whether the lesion is solid or cystic. It also helps in accurately guiding the FNAC needle to perform biopsy from the suspected lesion.

MetastasisMost metastases to the parotid or submandibular gland are from continuous spread of squamous cell carcinoma of the pharynx or neck. Hematogenous metastases have been described in carcinoma of the breast, neck, lung, and kidney and in metastatic melanoma. Despite the vascularity of the parotid gland, blood borne metastasis is rare. Lymphatic metastases to the parotid glands also are possible.

Malignant salivary gland tumours are staged using the TNM staging system: T : TumourTx : primary tumour cannot be assessedT0 : no evidence of primary tumourT1

less than or equal to 2cm in maximal diameterno extra-parenchymal extension

T22 - 4cm in maximal diameterno extra-parenchymal extension

T3greater than 4cm in maximal diameter ORany size with extra-parenchymal extension

T4A : direct extension into skin, mandible, ear canal, facial nerveT4B : direct extension into base of skull, pterygoid plates, or encases carotid artery.

N : NodesNx : nodes cannot be assessedN0 : no evidence of nodal involvementN1

single ipsilateral node< 3cm in maximal diameter

N2Asingle ipsilateral node3 - 6cm in maximal diameter

N2Bmultiple ipsilateral nodesless than 6cm in maximal diameter

N2Ccontralateral or bilateral nodesless than 6cm in maximal diameter

N3 : > 6cm in maximal diameterM : MetastasesMx : presence of metastases cannot be assessedM0 : no evidence of metastasesM1 : distant metastases present

Developmental anomalies.Aberrant salivary glands.An aberrant or ectopic is salivary gland tissue that develop at a site where it is not normally found.Aplasia and hypoplasia.Aplasia occurs in combination with congenital anomalies.Hypoplasia in patient with Melkersen Rosenthal syndrome.Hyperplasia.Accessory ducts. Most common developmental anomalies.Atresia, congenital occlusion or absence of one or two major salivary gland ducts.Diverticulae, small pouches of ductal system of one of the major salivary glands.Congenital fistula.

Non-contrast computed tomography axial sections demonstrate bilateral absence of parotid glands (long arrows) and bilateral submandibular glands (Figure a, small arrows). (c) Multiplanar Magnetic Resonance (MR) image, coronal sections demonstrates absence of bilateral submandibular glands (small arrows). (d) Multiplanar MR axial sections shows absence of bilateral parotid glands (small arrows).

Salivary gland scintigraphy (99mTcO4). There was no uptake of technetium after 5, 10, 20, 30 (stimulant administration), and 40 min in all major salivary glands.

Enhanced CT axial images in case 2. Axial images on the mandibular angle (A) and the mandibular foramen levels (B) showing the normal parotid gland on the right side (black arrows) and the absence of the parotid gland on the left side (white arrows). (C and D) Image on the condylar neck level shows the hypoplastic parotid gland (black arrows) overlying the masseter and the absence of the gland in the retromandibular parotid space (white arrow heads), compared with the normal parotid gland on the contralateral side (white arrows). The hypoplastic parotid gland (black arrows) could be enhanced during sialography (D). Also note the left maxillary mass (*).

Axial and coronal T2WI image showing hypoplastic left parotid gland with prominent fat. Right parotid gland appears normal.

Submandibular gland stone.

Plain radiographs.

Sialolithiasis, single (A) and multiple (B) in two different patients, as detected on CT. Small inset on the right (C) shows a multilayer structure that is observed in the majority of calculi (hydroxyapatite)

Submandibular calculi visualized at MR imaging. (a) Transverse T1-weighted SE MR image shows two areas of low signal intensity (arrows) in the floor of the mouth on the left. (b) These calculi (arrows) are confirmed on this transverse T2-weighted SE MR image, and the obstructed duct (arrowhead) is evident. Inflammation around the stones accounts for some peripheral high signal intensity. (c) The duct (arrowhead) can also be seen on this contrast-enhanced, T1-weighted, fat-saturated, spoiled gradient-echo MR image. The walls enhanced, presumably due to inflammation (sialodochitis). (d) There was coincidental sialadenitis of the left submandibular gland seen as enlargement and high signal intensity on this transverse, fat-saturated, T2-weighted fast SE MR image. Note intraglandular ductal dilatation (arrows).

Sialadenitis is bacterial infection of a salivary gland, usually due to an obstructing stone or gland hyposecretion. Symptoms are swelling, pain, redness, and tenderness. Diagnosis is clinical. CT, ultrasonography, and MRI may help identify the cause. Treatment is with antibiotics. EtiologySialadenitis usually occurs after hyposecretion or duct obstruction but may develop without an obvious cause. The major salivary glands are the parotid, submandibular, and sublingual glands. Sialadenitis is most common in the parotid gland and typically occurs in patients in their 50s and 60s, in chronically ill patients with xerostomia, in those with Sjögren syndrome, and in those who have had radiation therapy to the oral cavity. Adolescents and young adults with anorexia are also prone to this disorder. The most common causative organism is Staphylococcus aureus; others include streptococci, coliforms, and various anaerobic bacteria.Symptoms and SignsFever, chills, and unilateral pain and swelling develop. The gland is firm and diffusely tender, with erythema and edema of the overlying skin. Pus can often be expressed from the duct by compressing the affected gland and should be cultured. Focal enlargement may indicate an abscess.

Mumps is an acute, contagious, systemic viral disease, usually causing painful enlargement of the salivary glands, most commonly the parotids. Complications may include orchitis, meningoencephalitis, and pancreatitis. Diagnosis is usually clinical; all cases are reported promptly to public health authorities. Treatment is supportive. Vaccination is effective for prevention. The causative agent, a paramyxovirus, is spread by droplets or saliva. The virus probably enters through the nose or mouth. It is in saliva up to 7 days before salivary gland swelling appears with maximal transmissibility just before the development of parotitis. It is also in blood and urine and, if the CNS is involved, in CSF. One attack usually confers permanent immunity.

Mumps is less communicable than measles. It occurs mainly in unimmunized populations, but outbreaks among largely immunized populations have occurred. A combination of primary vaccine failure (failure to develop immunity after vaccination) and waning immunity may have played a part in these outbreaks.

Acute parotitis. US (longitudinal (A) and transverse (B)) shows an enlarged, hypoechoic gland with multiple hypoechogenic areas corresponding to acinic dilatations. Color Doppler register is increased (C).

Acute right-sided parotitis. Transverse, contrast-enhanced, fat-saturated, T1- weighted SE MR image shows marked enhancement of the right parotid gland (thick and thin arrows) compared with the left. The superficial subcutaneous tissue is also inflamed.

HIV-related lesions. Transverse, contrast-enhanced CT scan depicts a right sided parotid cyst (straight arrow) and multiple small nodules in the left parotid gland (curved arrow) in this patient who was HIV positive but had not fulfilled criteria for acquired immunodeficiency syndrome.

Sialolithiasis and sialadenitis, as seen on color Doppler ultrasound of the submandibular gland. Two small calculi, 2 and 3mm in size, respectively (arrows), are seen as hyperechoic structures with posterior shadowing. The increased vascularization of the slightly enlarged gland should be noted.

Recurrent sialadenitis of the parotid gland: ultrasound and magnetic resonance sialography findings.

Parotid sialadenitis.

Sialadenitis whit abscess. a) Axial T2-W. b) Axial T1. c) Axial postcontrast T1W show an ill-defined inhomogeneous signal intensity involving the left parotid gland with periferic enhanced and central necrosis. d, e) Transverse DW images obtained with a b factor of 0 s/mm2 and 1000 s/mm2 show a mass with high signal intensity. f) Axial ADC map shows lower signal intensity and the lesion was incorrectly diagnosed as a malignant lesion.

Viral parotitis (mumps) on US. Image A) represents the two pairs of glands on a longitudinal view, with pathological enlargement of the right parotid, whereas image B) shows the asymmetry in a transverse view.

Ranula: Postcontrast computed tomography study at the level of the floor of the mouth demonstrating a hypo attenuating cystic lesion in the left sublingual space extending into the submandibular space without enhancement, consistent with a plunging or diving ranula.

Plunging or cervical Ranula:

Left sublingual space extending to the submandibular space consistent with a plunging ranula (arrow).

Lipoma. Computed tomography scan through the left parotid demonstrates a fat-attenuation mass within the tail of the parotid gland.

Lipomas are common benign soft tissue neoplasms but they are found very rarely in the parotid gland. Surgical intervention in these tumors is challenging because of the proximity of the facial nerve, and thus knowledge of the anatomy and meticulous surgical technique are essential.

Lipomas. (a) Although the attenuation of this patient’s parotid glands is low due to fatty infiltration on this transverse CT scan, a palpable (see marker superficially) lipoma (L) in the left parotid gland was appreciated. (b) This lipoma (arrow), hyperintense on this transverse T1-weighted SE (600/11) MR image, was extraglandular but still contained by the deep cervical fascia surrounding the gland.

Sublingual gland epidermoid cyst (white arrows).

Contrast-enhanced coronal CT image (A) shows submandibular mucocele on right side (thick white arrow) while axial CT image (B) shows right sublingual gland mucocele (thin white arrows)

Left parotid hemangioma

Bilateral parotid hemangiomas.

Hemangioma as a hyperintense mass at the left parotid gland.

Sjögren syndrome in a 49-year-old woman. Computed tomography shows that the parotid glands are bilaterally diffusely enlarged and markedly heterogeneous in density, with a suggestion of multiple small lucencies.

Sjögren disease. While both parotid glands (arrowheads) show cystic changes in and enlargement of the gland on this coronal T2-weighted SE MR image, the left side also shows periparotid adenopathy (arrow).

Benign lymphoepithelial lesions (BLL or BLEL), also misleadingly known as AIDS-related parotid cysts (ARPC), are mixed solid and cystic lesions which enlarge the parotid glands, and are usually associated with cervical lymph node enlargement, and nasopharyngeal lymphofollicular hyperplasia. Despite their aforementioned alternative name, BLL are seen usually in HIV positive patients without AIDS, and are not an AIDS defining illness. It is relatively common in the HIV population, with 5% of patients eventually developing BLL.BLLs are only rarely seen in the submandibular glands or sublingual glands.Pathology:Thought to arise from dilatation of intraglandular ducts from obstruction due to lymphoid hypertrophy. They are bilateral in 20 % of cases.Radiographic features:well circumscribed cystic spaces, may demonstrate thin rim enhancement on post contrast MRI ultrasound demonstrates these 'cystic' lesions to actually have multiple small septations, and commonly also small mural nodules (40%)a vascular pedicle may be seen entering the cystic regionBLLs are usually seen associated with other sites of lymphoid hyperplasia , including: prominent nasopharyngeal adenoidal tissue : seen in 35% of HIV positive patients posterior triangle lymphadenopathy abnormal bone marrow signal.

Benign-lymphoepithelial-lesions-in-HIV.

Mycobacterium tuberculosis infection within the left parotid gland.

Two cases of primary parotid tuberculosis mimicking parotid neoplasm

Pleomorphic adenomas (also known as benign mixed tumour (BMT)) are the most common salivary gland tumours. EpidemiologyPleomorphic adenomas account for 70-80% of benign salivary gland tumours and are especially common in the parotid gland . Patients are typically in their middle age, and prior head and neck irradiation is a risk factor for the development of these tumours. Clinical presentationPatients typically present with a smooth painless enlarging mass. DistributionDistribution among the salivary glands is as follows: parotid gland - 84% : commoner in the superficial lobesubmandibular gland - 8%minor salivary glands - 6.5% widely distributed including the nasal cavity, pharynx, larynx, trachea sublingual glands - 0.5%

Radiographic featuresCT: Smoothly marginated or Lobulated homogeneous small spherical mass is the most common appearance. When larger they can be heterogeneous with foci of necrosis. Small regions of calcification are common .When small enhancement tends to be prominent. In larger tumours enhancement is less marked, but can demonstrate delayed enhancement.MRI: They are commonly seen as well-circumscribed and homogeneous when small. Larger tumours may be heterogeneous. T1 - usually of low intensityT2, usually of very high intensity (especially myxoid type)

often have a rim of decreased signal intensity on T2-weighted images representing the surrounding fibrous capsule

T1 C+ (Gd) - usually demonstrates homogeneous enhancementUltrasound: Typically hypoechoic. May show a lobulated distinct border +/- posterior acoustic enhancement.Ultrasound is also useful in guiding biopsy (both FNAC and core biopsies) but needs to be carried out with care to avoid facial nerve damage . Angiography (DSA): Typically hypovascular.

Pleomorphic adenoma of the right parotid A: Computed tomography (CT) and MRI shows a well-circumscribed low-density mass in the superficial lobe

Non-contrast T2 & T1W axial images (upper row) and T2W coronal & DW axial images (lower row) show pleomorphic adenoma of right parotid gland (white arrows).

Pleomorphic adenoma in left submandibular gland. US shows a homogeneous hypoechoic nodular lesion (*) inside the left submandibular gland. MR images show hyperintense lesion in T2, hypointense in T1 and with homogeneous enhancement after de endovenous gadolinium administration (arrows).

Pleomorphic adenoma in left submandibular gland. US shows a homogeneous hypoechoic nodular lesion (*) inside the left submandibular gland. MR images show hyperintense lesion in T2, hypointense in T1 and with homogeneous enhancement after de endovenous gadolinium administration (arrows).

A Warthin tumour (or papillary cystadenoma lymphomatosum) is a benign sharply demarcated tumour of the parotid gland. It is bilateral in 10-15% of cases. EpidemiologyThey are the 2nd most common (up to 10% of all parotid tumours) benign parotid tumour (after pleomorphic adenoma) and are the commonest bilateral or multifocal benign parotid tumour. It typically occurs in the elderly (6th decade). There is a recognised male predilection. Patients typically present with painless parotid swelling.MorphologyThey are often multi-centric (20%) and are usually small (1-4 cm). They have a typically heterogenous appearance on all modalities, often with cystic components (30%). LocationTends to favour the parotid tail region.

Warthin tumour

Radiographic featuresHas a greater tendency to undergo cystic change than any other salivary gland tumour .Ultrasound:Usually seen as a relatively well defined, ovoid, hyperechoic mass. In some cases anechoic internal cystic areas may be present. They are often hypervascular.CT:can be often seen bilaterally classic appearance is a cystic lesion posteriorly within the parotid with a focal tumour nodulerelatively well definedcystic changes appear as intra lesion at lower attenuation, no calcificationMRI:Well defined and can be bilateral. T1 - low to intermediate signal with cyst containing cholesterol components containing focal high signal.T2 - heterogenous and variable signal intensityC+ (Gd) - usually no contrast enhancement .Scintigraphy:Often shows uptake with Tc99-pertechnetate, thallium and FDG-PET.

Computed tomography of Warthin tumor. A: A large well-defined mass involves the superficial lobe of the left parotid gland. The mass enhances diffusely. B: At the level of the parotid tail, areas of lower density (arrowheads) are consistent with cystic components observed in the posterior aspect of the mass.

Bilateral Warthin Tumors of the Parotid Gland on contrast-enhanced CT

Bilateral Warthin tumors. Bilateral parotid masses (arrows) are seen on this transverse, contrast material-enhanced, fat-saturated T1-weighted spin-echo (SE) MR image. The multiplicity and location at the tail of the parotid gland (near the lower mandible) are typical features of this tumor

Magnetic resonance imaging of an oncocytoma in the right parotid tail.

A mucoepidermoid carcinoma is a tumour that usually occurs in the salivary glands. EpidemiologyMucoepidermoid carcinomas are seen throughout all adult age groups, but are most common in middle age (35-65 years of age) . However, it is the most common malignant salivary gland tumour of childhood . Overall, mucoepidermoid carcinomas account for : 2.8-15.5% of all salivary gland tumours

1-10% of all major salivary gland tumours6.5-41% of minor salivary gland tumours

In the parotid gland they are the most common malignant primary neoplasm. Clinical presentationMucoepidermoid carcinomas most frequently arise in the parotid gland, and presents as a painless swelling, with or without facial nerve involvement. These tumours can however be found anywhere there are salivary glands. Overall distribution across various glands is as follows :major salivary glands : 50%.

parotid gland : 40%.submandibular gland : 7%.sublingual gland : 3%.

minor salivary glands : 50%.

Radiographic features:Radiographic appearances largely depend on grade, making preoperative imaging important in planning and counseling. Ultrasound.Typically a well circumscribed hypoechoic, with an either part of completely cystic appearance. The lesion stands out against the relatively hyperechoic normal parotid gland.CT.Low grade tumours appear as well circumscribed masses, usually with cystic components. The solid components enhance, and calcification is sometimes seen. They have appearances similar to benign mixed tumours. High grade tumours on the other hand, have poorly defined margins, infiltrate locally and appear solid.MRI.Again, imaging is dependent on grade. Low grade tumours have similar appearances to benign mixed tumours :T1 - low to intermediate signal ; low signal cystic spacesT2 - intermediate to high signal ; cystic areas will be high signalT1 C+ (Gd) - heterogeneous enhancement of solid componentsHigh grade tumours on the other hand have lower signal on T2 and poorly defined margins and infrequent cystic areas.T1 - low to intermediate signalT2 - intermediate to low signal

Mucoepidermoid carcinoma. A: Postcontrast computed tomography axial image demonstrates a heterogeneously enhancing mass in the superficial lobe of the left parotid gland post to the ramus of the mandible. Note the irregular and ill-defined margins of the mass. B: T1-weighted axial image demonstrates the mass, which is isointense to muscle signal intensity. Note that the mass is well seen because of the hyperintense surrounding signal of the rest of the parotid gland. C: T2-weighted axial image demonstrates the mass to be of intermediate signal intensity. D: Postcontrast T1-weighted axial image without fat suppression. Note that the mass is not seen, as the enhancement of the mass is isointense to the rest of the parotid gland

Mucoepidermoid carcinoma. MR images show a lobulated discretely ill-defined margins tumor (arrow) with periferical enhancement, after the endovenous gadolinium administration, in the superficial lobe of the left parotid gland.

Acinic cell carcinoma. MR shows a well-delimited nodular lesion (arrow) inside accessory parotid gland, localized lateral to the masseter muscle (M). This lesion is hyperintense in T2, hypointense in T1 and with homogeneous enhancement after de endovenous gadolinium administration. The definitive diagnose was anatomopathological (cystic acinic cell carcinoma),

Computed tomography of a recurrent adenoid cystic carcinoma in a 49-year-old woman who had previous right submandibular gland resection. An irregularly infiltrating enhancing mass is seen in the floor of the mouth and parapharyngeal space. Anterior fatty infiltration indicates hypoglossal nerve invasion

Adenocarcinoma of the right parotid gland.

Carcinosarcoma of the left parotid gland.

Axial and coronal contrast enhanced CT. The patient had previous surgery for squamous cell carcinoma involving the parotid gland, these images demonstrate recurrence within the parotid space. Note the involvement of the skin.

Axial PET-CT images demonstrating FDG avid mass centered on the parotid gland, with an FDG avid metastatic lymph node evident on the right axial image

Lymphomas primary located in the salivary gland tissue are very rare and constitute about 2–5% of all salivary gland neoplasms. Most cases of lymphoma involve the major salivary glands, frequently the parotid (50–93%) and submandibular glands. These neoplasms may arise from an intra-parotid lymph node or in the gland itself. In the normal parotid gland there are intraglandular lymph nodes, that is why it is often difficult to make a distinction between lymphoma arising primarily in the salivary gland and those of the lymph node origin embedded in the salivary gland. If these lymph nodes are affected by a malignant lymphoma and the glandular parenchyma is not, then the lymphoma should be considered as nodal type. The differential diagnosis is not always easy to do because there are cases of lymphomas originated from intraglandular lymph nodes and with extensive parenchyma involvement. We consider a primary salivary gland lymphoma the cases in which the main disease occur here and the parenchyma of the gland is involved. The morphology and prognosis are similar for bothorigin places . Primary malignant lymphomas of the salivary gland are predominantly B-cell type lymphomas and they include MALT-lymphoma, follicular and diffuse large B-cell lymphoma. Salivary gland T-cell lymphomas are very rare . Anaplastic large cell lymphoma is one of the distinctive subtypes of non-Hodgkin’s lymphoma of the T-cell phenotype .

Non-contrast T1W axial images show intra-parotid adenopathy (white arrows) with altered appearance in a case of tuberculosis of left parotid gland.

Bilateral parotid gland MALT lymphoma in a patient with Sjögren’s and sicca syndrome

Metastasis.Most metastases to the parotid or submandibular gland are from continuous spread of squamous cell carcinoma of the pharynx or neck. Hematogenous metastases have been described in carcinoma of the breast, neck, lung, and kidney and in metastatic melanoma. Despite the vascularity of the parotid gland, blood borne metastasis is rare. Lymphatic metastases to the parotid glands also are possible.

Metastasis to the parotid glands

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