Учебники / Head_and_Neck_Cancer_Imaging

Neoplasms of the Sinonasal Cavities

inflammation is frequently present within the sinonasal cavity. Differentiating by imaging between a small focus of cancer and such non-neoplastic tissue changes may be very difficult. On MRI, the signal characteristics displayed by these various tissues may overlap with those of cancer (Loevner and

Sonners 2002).

Currently, no clear guidelines concerning the use of imaging methods in the posttreatment surveillance of sinonasal cancer patients are available. In a study on 51 patients treated by radical surgery for malignant sinonasal neoplasms, subclinical tumor recurrence was detected with higher sensitivity by imaging (CT or MRI) than by clinical-endoscopic evaluation (89.7% versus 68.7%); the false positive rate with imaging was higher (4.7% versus 1.4%). The accuracy of imaging was slightly higher, but not significantly different from that of clinical-endoscopic examination (92.1% versus 88.8%) (Farina et al. 2001).

While interpreting a follow-up study, attention should be paid not only to the original tumor bed, but also to neural crossroads, such as the pterygopalatine fossa; tumor recurrence may become manifest as a soft tissue mass at some distance from the primary localisation by perineural spread (see Fig. 11.9)

References

Ahmadi J, Hinton DR, Segall HD, et al. (1993) Dural invasion by craniofacial and calvarial neoplasms: MR imaging and histopathologic evaluation. Radiology 188:747–749

Aoki J, Sone S, Fujioka F, Terayama K, Ishii K, Karakida O, Imai S, Sakai F, Imai Y (1991) MR of enchondroma and chondrosarcoma: rings and arcs of Gd-DTPA enhancement. J Comput Assist Tomogr 15:1011–1016

Barnes L, Brandwein M, Som PM (2001) Diseases of the nasal cavity, paranasal sinuses, and nasopharynx. In: Barnes L (ed) Surgical pathology of the head and neck, 2nd edn. Marcel Dekker, New York, pp 509-513, 516–517

Bourjat P, Kahn JL, Braun JJ (1999) Imagerie des plasmocytomes solitaires maxillo-mandibulaires. J Radiol 80:859– 862

Buob D, Wacrenier A, Chevalier D, Aubert S, Quinchon JF, Gosselin B, Leroy X (2003) Schwannoma of the sinonasal tract: a clinicopathologic and immunohistochemical study of 5 cases. Arch Pathol Lab Med 127:1196–1199

Chang PC, Fischbein NJ, McCalmont TH, Kashani-Sabet M, Zettersten EM, Liu AY, Weissman JL (2004) Perineural spread of malignant melanoma of the head and neck: clinical and imaging features. AJNR Am J Neuroradiol 25:5–11

Commins DJ, Tolley NS, Milford CA (1998) Fibrous dysplasia and ossifying fibroma of the paranasal sinuses. J Laryngol Otol 112:964–968

Constantinidis J, Steinhart H, Koch M, Buchfelder M, Schaenzer

217

A, Weidenbecher M, Iro H (2004) Olfactory neuroblastoma: the University of Erlangen-Nuremberg experience 1975– 2000. Otolaryngol Head Neck 130:567–574

De Beuckeleer LH,De Schepper AM,Ramon F,Somville J (1995) Magnetic resonance imaging of cartilaginous tumors: a retrospective study of 79 patients. Eur J Radiol 21:34–40

De Vuysere S, Hermans R, Marchal G (2001) Sinochoanal polyp and its variant, the angiomatous polyp: MRI findings. Eur Radiol 11:55–58

Eisen MD, Yousem DM, Montone KT, et al. (1996) Use of preoperative MR to predict dural, perineural, and venous sinus invasion of skull base tumors. AJNR Am J Neurorad 17:1937–1945

Eisen MD, Yousem DM, Loevner LA, Thaler ER, Bilker WB, Goldberg AN (2000) Preoperative imaging to predict orbital invasion by tumor. Head Neck 22:456–462

El-Mofty S (2002) Psammomatoid and trabecular juvenile ossifying fibroma of the craniofacial skeleton: two distinct clinicopathologic entities. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 93:296–304

Farina D, Battaglia G, Maculotti P, Marconi A, Maroldi R (2001) Effectiveness of imaging in detecting subclinical recurrence in the follow-up of 51 treated nasosinusal malignancies. Eur Radiol 11 (S1):199 (abstract)

Ginsberg LE, DeMonte F (1998) Imaging of perineural tumor spread from palatal carcinoma. AJNR Am J Neuroradiol 19:1417–1422

Goffart Y, Jorissen M, Daele J, Vander Poorten V, Born J, Deneufbourg JM, Zicot AF, Remacle JM (2000) Minimally invasive endoscopic management of malignant sinonasal tumours. Acta Otorhinolaryngol Belg 54:221–232

Graamans K, Slootweg PJ (1989) Orbital exenteration in surgery of malignant neoplasms of the paranasal sinuses. Arch Otolaryngol Head Neck Surg 115:977–980

Heffner DK, Gnepp DR (1992) Sinonasal fibrosarcomas, malignant schwannomas, and “Triton” tumors. A clinicopathologic study of 67 cases. Cancer 70:1089–1101

Hermans R, Horvath M, De Schrijver T, Lemahieu SF, Baert AL (1994) Extranodal non-Hodgkin lymphoma of the head and neck. J Belge Radiol 77:72–77

Hermans R, De Vuysere S, Marchal G (1999) Squamous cell carcinoma of the sinonasal cavities. Semin Ultrasound CT MR 20:150–161

Herrmann BW, Sotelo-Avila C, Eisenbeis JF (2003) Pediatric sinonasal rhabdomyosarcoma: three cases and a review of the literature. Am J Otolaryngol 24:174–180

Jorissen M (1995) The role of endoscopy in the management of paranasal sinus tumours. Acta Otorhinolaryngol Belg 49:225–228

Kadish S, Goodman M, Wang CC (1976) Olfactory neuroblastoma: a clinical analysis of 17 cases. Cancer 37:1571– 1576

Kim HJ, Kim JH, Kim JH, Hwang EG (1995) Bone erosion caused by sinonasal cavernous hemangioma: CT findings in two patients. AJNR Am J Neuroradiol 16:1176–1178

Kim GE, Park HC, Keum KC, et al. (1999) Adenoid cystic carcinoma of the maxillary antrum. Am J Otolaryngol 20:77–84

Kim BS, Vongtama R, Juillard G (2004) Sinonasal undifferentiated carcinoma: case series and literature review. Am J Otolaryngol 25:162–166

Kraus DH, Lanzieri CF, Wanamaker JR, Little JR, Lavertu P (1992) Complementary use of computed tomography and

218

magnetic resonance imaging in assessing skull base lesions. Laryngoscope 102:623–629

Kraus DH, Andersen PE (1997) Anterior fossa craniofacial resection: techniques. In: Kraus DH, Levine HL (eds) Nasal neoplasia. Thieme, New York, pp 119–139

Lee HM, Kang HJ, Lee SH (2005) Metastatic renal cell carcinoma presenting as epistaxis. Eur Arch Otorhinolaryngol 262:69–71

Levine HL, Timen SM, Papsidero MJ (1997) Endoscopic management of nasal and sinus neoplasms. In: Kraus DH, Levine HL (eds) Nasal neoplasia, Thieme, New York, pp 175–181

Loevner LA, Sonners AI (2002) Imaging of neoplasms of the paranasal sinuses. Magn Reson Imaging Clin N Am 10:467–493

Lloyd GAS (1988) Epithelial tumours. In: Diagnostic imaging of the nose and paranasal sinuses. Springer Verlag, London, pp 95–110

Mancuso AA, Harnsberger HR, Dillon WP (1988) Paranasal sinuses, nasal cavity, and facial bones. In: Workbook for MRI and CT of the head and neck, 2nd edn. Williams & Wilkins, Baltimore, pp 56–76

Maroldi R, Farina D, Battaglia G, Maculotti P, Nicolai P, Chiesa A (1997) MR of malignant nasosinusal neoplasms. Frequently asked questions. Eur J Radiol 24:181–190

Matias C, Corde J, Soares J (1988) Primary malignant melanoma of the nasal cavity. J Surg Oncol 39:29–32

Medina JE, Ferlito A, Pellitteri PK, Shaha AR, Khafif A, Devaney KO, Fisher SR, O’Brien CJ, Byers RM, Robbins KT, Pitman KT, Rinaldo A (2003) Current management of mucosal melanoma of the head and neck. J Surg Oncol 83:116–122

Miyamoto CT, Brady LW, Markoe A, Salinger D (1991) Ameloblastoma of the jaw. Treatment with radiation therapy and a case report. Am J Clin Oncol 14:225–230

Miyamoto RC, Gleich LL, Biddinger PW, Gluckman JL (2000) Esthesioneuroblastoma and sinonasal undifferentiated carcinoma: impact of histological grading and clinical staging on survival and prognosis. Laryngoscope 110:1262–1265

Murphey MD, Smith WS, Smith SE, Kransdorf MJ, Temple HT (1999) (From the archives of the AFIP 1999) Imaging of musculoskeletal neurogenic tumors: radiologic-pathologic correlation. Radiographics 19:1253–1280

Nemzek WR, Hecht S, Gandour-Edwards R, et al. (1998) Perineural spread of head and neck tumors: how accurate is MR imaging? AJNR Am J Neuroradiol 19:701–706

Pasquini E, Sciarretta V, Farneti G, Modugno GC, Ceroni AR (2004) Inverted papilloma: report of 89 cases. Am J Otolaryngol 25:178–185

Parsons JT, Stringer SP, Mancuso AA, Million RR (1994) Nasal vestibule, nasal cavity, and paranasal sinuses. In: Million RR, Cassisi NJ (eds) Management of head and neck cancer:

R. Hermans

a multidisciplinary approach. J.B. Lippincott Company, Philadelphia, pp 551–598

Prasad ML, Busam KJ, Patel SG, Hoshaw-Woodard S, Shah JP, Huvos AG (2003) Clinicopathologic differences in malignant melanoma arising in oral squamous and sinonasal respiratory mucosa of the upper aerodigestive tract. Arch Pathol Lab Med 127:997–1002

Patel SG, Prasad ML, Escrig M, Singh B, Shaha AR, Kraus DH, Boyle JO, Huvos AG, Busam K, Shah JP (2002) Primary mucosal malignant melanoma of the head and neck. Head Neck 24:247–257

Regenbogen VS, Zinreich SJ, Kim KS, Kuhajda FP, Applebaum BI, Price JC, Rosenbaum AE (1988) Hyperostotic esthesioneuroblastoma: CT and MR findings. J Comput Assist Tomogr 12:52–56

Simon D, Somanathan T, Ramdas K, Pandey M (2003) Central mucoepidermoid carcinoma of mandible – a case report and review of the literature. World J Surg Oncol 1:1. doi:10.1186/1477–7819–1–1

Som PM, Shapiro MD, Biller HF, Sasaki C, Lawson, W (1988) Sinonasal tumors and inflammatory tissues: differentiation with MR imaging. Radiology 167:803-808

Suarez C, Llorente JL, Fernandez De Leon R, Maseda E, Lopez A (2004) Prognostic factors in sinonasal tumors involving the anterior skull base. Head Neck 26:136–144

Tart RP, Mukherji SK, Avino AJ, et al. (1993) Facial lymph nodes: normal and abnormal CT appearance. Radiology 188:695–700

Thompson LD, Gyure KA (2000) Extracranial sinonasal tract meningiomas: a clinicopathologic study of 30 cases with a review of the literature. Am J Surg Pathol 24:640–650

UICC, International Union Against Cancer (2002) TNM classification of malignant tumours, 6th edn. Wiley-Liss, New York, p 43–45

Vanhoenacker P, Hermans R, Sneyers W, Vanderperre H, Clarysse J, Loncke R, Baert AL (1993) Atypical aesthesioneuroblastoma: CT and MRI findings. Neuroradiology 35:466–467

Verbin RS, Appel BN (2001) Odontogenic tumors. In: Barnes L (ed) Surgical pathology of the head and neck, 2nd edn. Marcel Dekker, New York, pp 1557–1648

Wiseman SM, Popat SR, Rigual NR, Hicks WL Jr, Orner JB, Wein RO, McGary CT, Loree TR (2002) Adenoid cystic carcinoma of the paranasal sinuses or nasal cavity: a 40-year review of 35 cases. Ear Nose Throat J 81:510–517

Yousem DM, Fellows DW, Kennedy DW, Bolger WE, Kashima H, Zinreich SJ (1992) Inverted papilloma: evaluation with MR imaging. Radiology 185:501–505

Zwahlen RA, Grätz KW (2002) Maxillary ameloblastomas: a review of the literature and of a 15-year database. J Craniomaxillofac Surg 30:273–279

CONTENTS

12.1Introduction 219

12.2Anatomy 219

12.3Imaging Issues 220

12.4.1Benign Mixed Tumor or Pleomorphic Adenoma 221

12.4.1.1General Description 221

12.4.1.2Histological Findings 221

12.4.1.3Imaging Findings 222

12.4.1.4Differential Diagnosis 222

12.4.2Warthin’s Tumor or Papillary Cystadenoma

Lymphomatosum 222

12.4.2.1 General Description 222

12.4.2.2Histological Findings 225

12.4.2.3Imaging Findings 225

12.4.2.4Differential Diagnosis 228

12.4.3 Other Benign Tumors 228

12.4.3.1Lipoma 228

12.4.3.2Neurogenic Tumor 228

12.4.4Congenital Tumors 228

12.4.4.1Lymphangioma 228

12.4.4.2Infantile Hemangioma 228

12.4.5Cystic Tumors 229

12.5.1Histologic Classification 231

12.5.2Imaging Findings 231

12.5.2.1Parotid Cancer 231

12.5.2.2Non-Hodgkin Lymphoma 234

12.6Difficult Cases 234

12.7.1Sjögren’s Syndrome 235

12.7.2Sarcoidosis 236

12.9Conclusion 239 References 241

F. Dubrulle, MD; R. Souillard, MD

Plateau Technique d’Imagerie, Hôpital Huriez Sud, CHU Lille, 59000 Lille, France

12.1 Introduction

The parotid gland is the largest salivary gland. It is located in the parotid space. The parotid gland can be affected by a variety of pathologic processes, especially neoplastic. Parotid tumors represent less than 3% of all head and neck tumors and are most frequently benign. These tumors require surgery in most cases and imaging is essential in the work-up of these lesions.

12.2 Anatomy

The parotid space is a paired lateral suprahyoid neck space surrounded by the superficial layer of the deep cervical fascia. This space extends from the external auditory canal and the mastoid tip superiorly to the angle of the mandible below. It contains the parotid gland, intraand extra-parotid lymph nodes. The gland contains about 20 intraglandular lymph nodes which are considered normal if their transverse diameter is less than 8 mm. The gland also contains extracranial branches of the facial nerve, and vessels: the external carotid artery and the retromandibular vein just behind the mandibular ramus (Fig. 12.1).

The facial nerve exits the skull base via the stylomastoid foramen and continues within the parotid gland from its posterior and superior part to its anterior and inferior part, lateral to the retromandibular vein. It then divides into superior temporofacial branches and inferior cervical branches. By convention, the facial nerve is used as a reference plane within the gland to separate the external superficial lobe and the internal deep lobe, but actually there is no true anatomic division. The facial nerve is not seen with imaging and its course can only be estimated (Fig. 12.1) (Harnsberger 2004).

The parotid space is directly lateral to the anterior part of the parapharyngeal space (prestyloid space),

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Fig. 12.1. Anatomy of the parotid space. The parotid space (outlined in red) is made of the parotid gland, the retromandibular vein (blue circle), the external carotid artery (red circle) and intraand extra-parotid lymph nodes. It also contains the facial nerve, which is not directly seen on imaging; it is used as a reference plane (green line) to separate the parotid gland into an external superficial lobe and an internal deep lobe

F. Dubrulle and R. Souillard

Fig. 12.2. Lateral and internal to the parotid space is the anterior part of the parapharyngeal space (or prestyloid compartment) (both outlined in red); there is no real anatomic division between these two spaces. The most internal part of the deep parotid lobe bulges in the prestyloid compartment. Posterior (retrostyloid) part of the parapharyngeal space, also called the carotid space (outlined in green), separated from the anterior parapharyngeal space by the styloid process (indicated in yellow), as well as muscles and a fascial layer originating from it (see also Chap. 9). Masticator space (outlined in blue)

without real anatomic division between these two spaces. The deep portion of the parotid gland bulges in the prestyloid compartment in which deep lobe tumors can extend (Fig. 12.2). The prestyloid compartment also contains fat tissue, accessory salivary glands and a prestyloid branch of the mandibular nerve (V3).

Anterior to the parotid space is the masticator space or infratemporal fossa, which contains the pterygoid muscles.

Posterior to the prestyloid parapharyngeal space is the carotid space or retrostyloid parapharyngeal space (Fig. 12.2).

There is an anatomic division between these different spaces (the masticator space, the carotid space and the anterior parapharyngeal space). Benign tumors will respect these anatomic limits whereas they will be infiltrated by malignant tumors.

The parotid gland also contains salivary ducts. The main parotid duct, or Stensen’s duct, emerges from the anterior part of the parotid gland, runs over the masseter muscle and in the superficial cervical fascia and then abruptly courses medially to pierce the buc-

cinator muscle, forming a nearly 90q angle with this muscle, terminating in the buccal mucosa at the level of the second upper molar (Fig. 12.3).

12.3

Imaging Issues

When a patient presents with a palpable mass of the parotid space, the radiologist has to answer several key questions, which are essential to the head and neck surgeon in order to determine the best therapy (Harnsberger 2004; Shah 2002; Vogl et al. 1999): x Is the mass intraor extraparotid? Small, intra-

parotid masses are easy to identify. For large and deep lobe masses, the knowledge of the different cervical spaces is essential. The pattern of displacement of the prestyloid parapharyngeal space has to be analyzed.

x Is the parotid space mass single or multiple? Unilateral or bilateral? Multiple lesions are suggestive

Fig. 12.3. The main parotid salivary duct canal or Stensen’s duct (red) emerges from the anterior part of the parotid gland, runs over the masseter muscle and in the superficial cervical fascia, then forms a 90q angle (arrow), pierces the buccinator muscle to terminate in the oral cavity at level of the second upper molar

for specific tumors: for example, bilateral tumors are suggestive of Warthin’s tumor, multiple cystic formations suggest Sjögren’s syndrome or benign lymphoepithelial lesions possibly related to HIV. x Does the tumor show benign or malignant characteristics? The surgical approach will depend on these characteristics. If malignancy is suspected, is there evidence of perineural spread along the facial nerve or branches of the trigeminal nerve? In that

case, the therapeutic attitude will be different.

x Is the tumor limited to the superficial lobe of the parotid? A superficial parotidectomy is sufficient for a benign, well-circumscribed, superficial lobe lesion. On the other hand, a superficial lesion extending in the deep lobe requires a total parotidectomy (O’Brien 2003).

x What is the relationship of the mass to the facial nerve? The facial nerve is not seen on imaging but its intraparotid course can be estimated (plane between the stylomastoid foramen and the lateral border of the retromandibular vein).

x Is it possible to determine the histologic type of a benign tumor? A pleomorphic adenoma of the parotid gland will require surgery, whereas Warthin’s tumor in elderly patients may be followed up clinically and by imaging.

In order to answer all these key questions, MR imaging is the primary modality of choice for parotid gland tumors (Joe and Westesson 1994; Shah 2004).

The classical sequences used are: axial and coronal turbo spin-echo T2-weighted and spin-echo T1weighted sequences with a slice thickness of 2–3 mm and a spin-echo T1-weighted sequence after contrast administration. A sequence with fat saturation after contrast administration is useful to better visualise potential perineural extension along the facial nerve or intracranial extension. This sequence is also useful to analyze correctly the tumoral enhancement.

A sequence to analyze the cervical lymph nodes is necessary if a malignant tumor is suspected. MR sialography can be useful if a pseudo-tumoral pathology such as Sjögren syndrome is suspected.

Diffusion-weighted sequence with calculation of an ADC map may be interesting to better characterize non specific tumors (Ikeda et al. 2004).

12.4

Benign Parotid Tumors

Benign tumors of the parotid gland represent about 85% of all parotid tumors (Okahara et al. 2003).

12.4.1

Benign Mixed Tumor or Pleomorphic Adenoma

12.4.1.1

General Description

This is the most common parotid gland tumor and it represents 70%–80% of all tumors of the parotid gland. The lesion is usually solitary. Of all pleomorphic adenomas, 90% occur in the superficial lobe. If the lesion originates from the deep lobe, it can become large, extending in the anterior parapharyngeal space without causing symptoms.

There is a female predominance (sex ratio: 2/1). Facial nerve paralysis is uncommon.

12.4.1.2

Histological Findings

Pleomorphic adenoma is encased in a capsule that may be incomplete. It contains epithelial, myoepithelial and stromal (mucoid, myxoid, chondroid) cellular components. Calcifications are rare. Sites of cystic

changes and hemorrhage may be present, especially if the tumor is large.

The lesion may show multicentric outgrowths through its capsule. For this reason, partial parotidectomy is recommended whenever a pleomorphic adenoma is suspected, provided the tumor can be removed with a safe margin. The risk of recurrence is very high when only an enucleation of the tumor is performed. In some centers, even total parotidectomy is routinely performed for pleomorphic adenoma, in order to limit the risk of recurrence as much as possible.

12.4.1.3

Imaging Findings

x Typically, pleomorphic adenoma is a solitary, wellcircumscribed mass.It may be lobulated.This tumor has low T1-weighted and high T2-weighted signal intensities. It may demonstrate a low T2-weighted signal intensity capsule. It shows homogeneous enhancement on T1 contrast-enhanced images, well illustrated on delayed contrast-enhanced T1weighted images with fat saturation (Figs. 12.4, 12.5) (Ikeda et al. 1996). Imaging findings may be less typical in the case of larger tumors, but the lesion remains lobulated and well-circumscribed. Areas of hemorrhage appear as regions of high signal intensity on both T1and T2-weighted images (Fig. 12.6). Myxoid degeneration appears as heterogeneous and intermediate T2-weighted signal intensity (Fig. 12.7). In these large tumors, signal intensity can be heterogeneous on early contrast-enhanced images but it can appear more homogeneous on delayed contrast-enhanced, fat-suppressed T1weighted images (Fig. 12.4). An extension to the deep lobe of the parotid gland must be looked for and reported. Large tumors of the deep lobe are usually mixed tumors (Figs. 12.8, 12.9).

x Non-typical forms of pleomorphic adenoma are rare. These lesions have a low T2-weighted signal intensity which corresponds to fibrous tissue (Fig. 12.10). The correct diagnosis may be difficult but a solitary, well-circumscribed, encapsulated lesion is suggestive of benign tumor (Harnsberger 2004).

x Calcified lesions are uncommon; these calcifications occur after a long evolution.

x Recurrent pleomorphic adenoma tends to be multifocal and more aggressive (Fig. 12.11).

x Malignant degeneration within a pleomorphic adenoma is rare but exists. The most common type of malignancy associated with pleomorphic

adenoma is a carcinoma ex pleomorphic adenoma, or sometimes an adenocarcinoma. Malignant characteristics are then present on imaging studies (see below).

12.4.1.4

Di erential Diagnosis

x Warthin’s tumor or papillary cystadenoma lymphomatosum. Especially in the case of non-typi- cal imaging findings of pleomorphic adenoma (see Sect. 12.6 below).

x Malignant tumor. Features suggesting malignancy are heterogeneous enhancement, an infiltrating mass with irregular margins, perineural tumor spread or infiltration of adjacent fat tissue.

x Non-Hodgkin lymphoma of the parotid gland. The clinical presentation may be suggestive (see below and Chap. 16).

x Parotid nodal metastasis (often from skin carcinoma or melanoma, sometimes systemic metastasis).

12.4.2

Warthin’s Tumor or Papillary Cystadenoma Lymphomatosum

12.4.2.1

General Description

This is the second most frequent benign tumor arising in the parotid gland and it represents 10%–25% of all parotid tumors.

It is more common in males than in females (sex ratio: 3/1). The mean age at presentation is 60 years old. About 90% of patients with this tumor are cigarette smokers. This diagnosis should not be suggested before the age of 40 years old (Harnsberger 2004).

It arises almost exclusively in the lower portion of the superficial lobe of the parotid gland. There is a bilateral involvement in 15%–20% of patients, which presents simultaneously or metachronously,the contralateral location may be discovered on imaging only.

These are slow-growing tumors and malignant transformation is uncommon, occurring in less than 1% of Warthin’s tumors.

The recommended treatment is superficial parotidectomy, sparing the intraparotid facial nerve. Considering the slow-growing nature of this tumor and its very low risk of degeneration, a clinical and radiological follow-up can be proposed especially in elderly people in whom the diagnosis of Warthin’s tumor is suspected on imaging.

Parotid Gland and Other Salivary Gland Tumors

Fig. 12.7. Pleomorphic adenoma of the left parotid gland with a high T2-weighted signal intensity and small heterogeneous areas of lower signal intensity, related to myxoid degeneration (arrow). The capsule is well identified (arrowhead)

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Fig. 12.8. Pleomorphic adenoma extending to the left anterior parapharyngeal space with typical high signal on T2-weighted images

Fig. 12.9. Large pleomorphic adenoma of the deep lobe of the right parotid gland with non-homogeneous, high signal intensity on this T2-weighted image. Larger tumors typically show slightly heterogeneous signal intensity

12.4.2.2

Histological Findings

The papillary cystadenoma lymphomatosum is encapsulated. It arises within the lymphoid tissue of the parotid gland and is composed of lymphoid stroma and epithelium. The epithelial component is characterized by cystic spaces; it can show hemorrhagic areas. For these reasons, Warthin’s tumors tend to be nonhomogeneous on imaging.

12.4.2.3

Imaging Findings

Warthin’s tumor has typically a heterogeneous appearance on imaging, due to cystic and hemorrhagic changes, with overall benign characteristics: a wellcircumscribed lesion measuring 2–4 cm in diameter.

The tumor has low T1-weighted signal intensity,with small areas of high signal intensities due to accumulation of proteinous fluid, cholesterol crystals or hemorrhagic changes. Such areas are seen in about 60% of the cases and are typical of the diagnosis of Warthin’s tumor (Figs. 12.12, 12.13) (Ikeda et al. 2004).

The tumor has intermediate and high T2-weighted signal intensities. The high signal intensities areas correspond to cystic foci.

It shows a mild enhancement on contrast-en- hanced T1-weighted images. Cystic spaces show no enhancement. A typical aspect of the tumor is a ring enhancement (Fig. 12.12). Fat-suppressed, contrastenhanced T1-weighted images illustrate better the heterogeneous enhancement of the tumor.

Multiple lesions in one parotid gland or bilaterally have to be looked for. Bilateral lesions in the lower parts of the parotid glands are virtually pathognomonic (Figs. 12.13, 12.14).

Warthin’s tumor may extend to the deep lobe of the parotid gland (Fig. 12.13). On the other hand, a primary location in the deep lobe is very rare.

On diffusion-weighted imaging, Warthin’s tumors present a low ADC value (Ikeda et al. 2004).