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---
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title: "Parotid Schwannoma"
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docid: "039d782c-2e1e-455f-9cdc-dc00dc65c750"
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authors:
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||||
- key: "639a3888-2423-42a0-ba09-67dd25a0b4f3"
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value: "Lisa J. Koenig, BChD, DDS, MS"
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value: "Hilda E. Stambuk, MD"
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breadcrumbs:
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name: "Head and Neck"
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slug: "head-and-neck"
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-
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name: "Benign Tumors"
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slug: "benign-tumors"
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name: "Parotid Schwannoma"
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slug: "parotid-schwannoma"
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category: "Head and Neck"
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documentVersionId: "6cdd8d8b-0709-4b72-ab2f-6753af1f7bce"
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imageCount: 8
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lastUpdated: "08/02/23"
|
||||
pageDescription: "Parotid Schwannoma"
|
||||
pageKeywords: "Head and Neck, Diagnosis, Parotid Space, Benign Tumors, Parotid Schwannoma"
|
||||
pageTitle: "Parotid Schwannoma | STATdx"
|
||||
enhancedTitle: "Parotid Schwannoma"
|
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type: "DX"
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references: true
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anatomy:
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- "{'authors': 'Surjith Vattoth, MD, FRCR', 'bookmarked': False, 'bookmarkUrl': '/document/bookmark/50ac1eaf-3866-4ebd-8f5c-437055a64ba4', 'category': 'Head and Neck', 'compareUrl': '/compare/document/50ac1eaf-3866-4ebd-8f5c-437055a64ba4/related-anatomy/treeNode?subContext=Suprahyoid and Infrahyoid Neck Overview', 'documentId': '50ac1eaf-3866-4ebd-8f5c-437055a64ba4', 'documentType': 'ANATOMY', 'documentUrl': '/document/suprahyoid-and-infrahyoid-neck-ove-/50ac1eaf-3866-4ebd-8f5c-437055a64ba4', 'enhancedTitle': 'Suprahyoid and Infrahyoid Neck Overview', 'entryDate': '02/19/24', 'imageCount': 47, 'imageUrl': '/image/thumbnail/bf5e5efb-e616-4aad-a2f1-6668016bb91a?size=174&quality=85', 'inCompareCart': False, 'rank': 2, 'referenceCount': 0, 'showCompareButton': False, 'title': 'Suprahyoid and Infrahyoid Neck Overview'}"
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- "{'authors': 'Santhosh Gaddikeri, MD; Philip R. Chapman, MD', 'bookmarked': False, 'bookmarkUrl': '/document/bookmark/98cb2d45-e64c-4295-9662-3470cd46513a', 'category': 'Head and Neck', 'compareUrl': '/compare/document/98cb2d45-e64c-4295-9662-3470cd46513a/related-anatomy/treeNode?subContext=CNVII (Facial Nerve)', 'documentId': '98cb2d45-e64c-4295-9662-3470cd46513a', 'documentType': 'ANATOMY', 'documentUrl': '/document/cnvii-facial-nerve/98cb2d45-e64c-4295-9662-3470cd46513a', 'enhancedTitle': 'CNVII (Facial Nerve)', 'entryDate': '12/06/23', 'imageCount': 39, 'imageUrl': '/image/thumbnail/1f7e56c2-da7a-4445-ac01-44eee0776f17?size=174&quality=85', 'inCompareCart': False, 'rank': 4, 'referenceCount': 0, 'showCompareButton': False, 'title': 'CNVII (Facial Nerve)'}"
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cases: 2
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breadcrumbs:
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- "Head and Neck"
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- "Diagnosis"
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- "Parotid Space"
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- "Benign Tumors"
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- "Parotid Schwannoma"
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---
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# KEY FACTS
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- ## Terminology
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- Benign nerve sheath neoplasm from Schwann cells of intraparotid facial nerve (CNVII)
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- ## Imaging
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- Heterogeneously enhancing tumor with intramural cystic areas when large
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- Cystic areas may be small, multifocal, or large
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- May extend toward or into stylomastoid foramen
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- Presence of **target sign** suggestive if present
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- Similar to schwannomas in other anatomic locations
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- ## Top Differential Diagnoses
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- Parotid benign mixed tumor
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- Warthin tumor
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- Parotid metastatic nodal disease
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- Parotid mucoepidermoid carcinoma
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- Perineural tumor spread, CNVII
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- ## Pathology
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- < 10% CNVII schwannoma = extratemporal (intraparotid), remaining = intratemporal or intracranial
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- Type A: Exophytic off CNVII branch; no CNVII resection required
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- Type B: Intrinsic to facial nerve branch; branch resection required
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- Type C: Intrinsic to facial nerve trunk; resection & reconstruction required
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- Type D: Encases main trunk & branches; resection & reconstruction required
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- ## Clinical Issues
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- Presents like any parotid mass; difficult to differentiate clinically or radiographically
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- Facial nerve palsy uncommon
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- Associated with neurofibromatosis type 2
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- Treatment goal: Preserve facial nerve function
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- Controversial: Observation vs. surgery vs. radiation
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# TERMINOLOGY
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- ## Synonyms
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- Facial neurilemmoma, intraparotid neurilemmoma
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- ## Definitions
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- Benign nerve sheath neoplasm from Schwann cells of intraparotid facial nerve (CNVII)
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# IMAGING
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- ## General Features
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- ### Best diagnostic clue
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- Heterogeneously enhancing + **intramural cysts**
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- Cystic areas may be small, multifocal, or large
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- ### Location
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- Course of intraparotid CNVII ± stylomastoid foramen
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- ### Morphology
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- Round or elongated along course of CNVII
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- ## Imaging Recommendations
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- ### Best imaging tool
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- T1WI C+ FS MR best demonstrates cystic areas
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- FS useful for distinguishing tumor enhancement from intraparotid fat
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- ## CT Findings
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- ### CECT
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- Well-defined, round or oval intraparotid mass
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- Intramural cysts within larger (> 2-cm) lesions
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- Enlarged stylomastoid foramen in proximal lesions
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- ## MR Findings
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- ### T1WI
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- Tumor isointense to muscle, well defined
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- ### T2WI
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- Slightly hyperintense to brain, muscle
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- Larger lesions with high-intensity cysts
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- **Target sign** (hypointense center with hyperintense fluid rim) suggestive if present
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- ### T1WI C+ FS
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- Enhancing & cystic regions + peripheral enhancement
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# DIFFERENTIAL DIAGNOSIS
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- [Parotid Benign Mixed Tumor](/document/parotid-benign-mixed-tumor/619fefa6-2266-494d-9a80-3fd2b21debcf)
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- Difficult to distinguish preoperatively
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- Appears similar to schwannoma on CT & MR
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- Benign mixed tumor classically with bosselated margins
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- Parotid schwannoma usually mistaken for benign mixed tumor
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- [Warthin Tumor](/document/warthin-tumor/1fd4b7da-113d-4bee-b431-4111d65055ce)
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- Cystic areas present as in schwannoma
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- Can be multiple, bilateral, & favor parotid tail
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- [Parotid Metastatic Nodal Disease](/document/metastatic-disease-of-parotid-node-/df446621-cdbb-4654-bee4-8bad10e81bdf)
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- Often multiple; have primary lesion (e.g., skin, lymphoma)
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- [Parotid Mucoepidermoid Carcinoma](/document/parotid-mucoepidermoid-carcinoma/74ed7ee4-5869-49f5-a28e-638a04849ce8)
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- Low-grade form of mucoepidermoid carcinoma
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- Well defined
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- ## Perineural Tumor Spread, CNVII
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- Parotid or skin primary lesion
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# PATHOLOGY
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- ## General Features
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- ### Etiology
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- Arises from differentiated neoplastic Schwann cells of CNVII nerve sheath
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- < 10% CNVII schwannoma = extratemporal (intraparotid), remaining = intratemporal or intracranial
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- ### Associated abnormalities
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- Multiple schwannomas are associated with neurofibromatosis type 2
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- ## Staging, Grading, & Classification
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- Type A: Exophytic off CNVII branch; no CNVII resection required
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- Type B: Intrinsic to CNVII branch; branch resection required
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- Type C: Intrinsic to CNVII trunk; resection & reconstruction required
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- Type D: Encases main CNVII trunk & branches; resection & reconstruction required
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- ## Gross Pathologic & Surgical Features
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- Smooth, rubbery, yellow, encapsulated fusiform mass
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- May arise eccentrically from CNVII
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- ## Microscopic Features
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- Same as schwannomas in other anatomic locations
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- Spindle cells with elongated nuclei
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- Divided into regions of Antoni A (compact cells) & Antoni B (loose clusters)
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- Predicts regional enhancement
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- No necrosis; intramural cysts
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- Immunochemistry: Strong, diffuse immunostaining for S100 protein = neural crest marker antigen present in supporting cells of nervous system
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# CLINICAL ISSUES
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- ## Presentation
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- ### Most common signs/symptoms
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- Painless, slowly enlarging cheek mass
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- Often asymptomatic for > 10 years
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- ### Other signs/symptoms
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- Presents like any parotid mass; difficult to differentiate clinically or radiographically
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- Rarely diagnosed preoperatively unless biopsied
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- CNVII palsy uncommon: ↑ risk if intratemporal extension
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- Associated with neurofibromatosis type 2
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- ## Demographics
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- Age: Can affect any age group
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- Most frequent in 4th & 5th decades
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- Earlier in patients with neurofibromatosis
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- ## Natural History & Prognosis
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- Slow growth; typically 0.5-2.0 mm/year
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- May eventually cause mass effect or cosmetic issues
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- ## Treatment
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- Controversial: Observation vs. surgery vs. radiation
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- Depends on CNVII function & location of tumor
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- Goal: CNVII function preservation & facial cosmesis
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- Can dissect tumor off nerve but may cause CNVII palsy
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- Types C & D lesions at ↑ risk of postoperative CNVII palsy
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- Stereotactic radiosurgery may be used if CNVII intact
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# DIAGNOSTIC CHECKLIST
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- ## Consider
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- Which branch of facial nerve involved
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- Main trunk most common
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- Relationship of mass to stylomastoid foramen
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- Extent into mastoid segment of bony facial nerve canal
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- ## Image Interpretation Pearls
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- Difficult to make radiographic diagnosis
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- Tissue sampling required but excisional biopsy risky
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- Image-guided biopsy (CT or US) very useful
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- Core needle biopsy required (fine-needle aspiration inadequate)
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788f9901-75ea-42a0-91d6-4b9e114708fb
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## References
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# Selected References
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1. [Behera P et al: Aspiration cytology of facial nerve schwannoma of parotid gland: a rare diagnosis. Cytopathology. 33(5):618-21, 2022](http://www.ncbi.nlm.nih.gov/pubmed/?term=35385173%5Bpmid%5D)
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1. [Jiang JY et al: A giant schwannoma extending from medial portion of middle cranial fossa to parapharyngeal space and deep parotid space. Ear Nose Throat J. ePub, 2022](http://www.ncbi.nlm.nih.gov/pubmed/?term=35349782%5Bpmid%5D)
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1. [Malić M et al: Multicentric intra/extracranial cystic facial nerve schwannoma: case report and review of literature. Indian J Otolaryngol Head Neck Surg. 74(Suppl 3):3872-6, 2022](http://www.ncbi.nlm.nih.gov/pubmed/?term=36742915%5Bpmid%5D)
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1. [Shamim M et al: Giant facial nerve schwannoma with extra-temporal involvement: a series of two cases. Indian J Otolaryngol Head Neck Surg. 74(Suppl 3):4399-404, 2022](http://www.ncbi.nlm.nih.gov/pubmed/?term=36742768%5Bpmid%5D)
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1. [Singh AK et al: Systematic review of intra parotid facial nerve schwannoma and a case report. Indian J Otolaryngol Head Neck Surg. 74(Suppl 3):6268-84, 2022](http://www.ncbi.nlm.nih.gov/pubmed/?term=36742919%5Bpmid%5D)
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1. [Bartindale M et al: Facial schwannoma management outcomes: a systematic review of the literature. Otolaryngol Head Neck Surg. 163(2):293-301, 2020](http://www.ncbi.nlm.nih.gov/pubmed/?term=32228141%5Bpmid%5D)
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||||
1. [Seo BF et al: Intraparotid facial nerve schwannomas. Arch Craniofac Surg. 20(1):71-4, 2019](http://www.ncbi.nlm.nih.gov/pubmed/?term=30703867%5Bpmid%5D)
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1. [Carlson ML et al: Facial nerve schwannomas: review of 80 cases over 25 years at Mayo Clinic. Mayo Clin Proc. 91(11):1563-76, 2016](http://www.ncbi.nlm.nih.gov/pubmed/?term=27720200%5Bpmid%5D)
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||||
1. [Zhang GZ et al: Clinical retrospective analysis of 9 cases of intraparotid facial nerve schwannoma. J Oral Maxillofac Surg. pii: S0278-2391(16)00165-8, 2016](http://www.ncbi.nlm.nih.gov/pubmed/?term=26973226%5Bpmid%5D)
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||||
1. [Bartindale M et al: The natural history of facial schwannomas: a meta-analysis of case series. J Neurol Surg B Skull Base. 80(5):458-68, 2019](http://www.ncbi.nlm.nih.gov/pubmed/?term=31534886%5Bpmid%5D)
|
||||
1. [McCarthy WA et al: Intraparotid schwannoma. Arch Pathol Lab Med. 138(7):982-5, 2014](http://www.ncbi.nlm.nih.gov/pubmed/?term=24978928%5Bpmid%5D)
|
||||
1. [Nader ME et al: Facial nerve paralysis due to a pleomorphic adenoma with the imaging characteristics of a facial nerve schwannoma. J Neurol Surg Rep. 75(1):e84-8, 2014](http://www.ncbi.nlm.nih.gov/pubmed/?term=25083397%5Bpmid%5D)
|
||||
1. [De Ceulaer J et al: Intraparotid facial nerve schwannoma: case report and literature review. B-ENT. 8(3):225-8, 2012](http://www.ncbi.nlm.nih.gov/pubmed/?term=23113388%5Bpmid%5D)
|
||||
1. [Gross BC et al: The intraparotid facial nerve schwannoma: a diagnostic and management conundrum. Am J Otolaryngol. 33(5):497-504, 2012](http://www.ncbi.nlm.nih.gov/pubmed/?term=22185683%5Bpmid%5D)
|
||||
1. [Ma Q et al: Diagnosis and management of intraparotid facial nerve schwannoma. J Craniomaxillofac Surg. 38(4):271-3, 2010](http://www.ncbi.nlm.nih.gov/pubmed/?term=19692254%5Bpmid%5D)
|
||||
1. [Alicandri-Ciufelli M et al: Critical literature review on the management of intraparotid facial nerve schwannoma and proposed decision-making algorithm. Eur Arch Otorhinolaryngol. 266(4):475-9, 2009](http://www.ncbi.nlm.nih.gov/pubmed/?term=19096863%5Bpmid%5D)
|
||||
1. [Guzzo M et al: Schwannoma in the parotid gland. Experience at our institute and review of the literature. Tumori. 95(6):846-51, 2009](http://www.ncbi.nlm.nih.gov/pubmed/?term=20210258%5Bpmid%5D)
|
||||
1. [Tanna N et al: Intraparotid facial nerve schwannoma: clinician beware. Ear Nose Throat J. 88(8):E18-20, 2009](http://www.ncbi.nlm.nih.gov/pubmed/?term=19688704%5Bpmid%5D)
|
||||
1. [Mehta RP et al: Intraoperative diagnosis of facial nerve schwannoma at parotidectomy. Am J Otolaryngol. 29(2):126-9, 2008](http://www.ncbi.nlm.nih.gov/pubmed/?term=18314025%5Bpmid%5D)
|
||||
1. [Salemis NS et al: Large intraparotid facial nerve schwannoma: case report and review of the literature. Int J Oral Maxillofac Surg. 37(7):679-81, 2008](http://www.ncbi.nlm.nih.gov/pubmed/?term=18339519%5Bpmid%5D)
|
||||
1. [Marchioni D et al: Intraparotid facial nerve schwannoma: literature review and classification proposal. J Laryngol Otol. 121(8):707-12, 2007](http://www.ncbi.nlm.nih.gov/pubmed/?term=17381883%5Bpmid%5D)
|
||||
1. [Ciko Z: [Current treatment of acute leukemias.] Vojnosanit Pregl. 26(11):563-6, 1969](http://www.ncbi.nlm.nih.gov/pubmed/?term=5198300%5Bpmid%5D)
|
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## Anatomy
|
||||
|
||||
### Facial Nerve (CNVII)
|
||||
Brain/ANATOMY:2f4818dd-6438-405b-8561-5cbbb9c91562
|
||||
|
||||
### Suprahyoid and Infrahyoid Neck Overview
|
||||
Head and Neck/ANATOMY:50ac1eaf-3866-4ebd-8f5c-437055a64ba4
|
||||
|
||||
### Parotid Space
|
||||
Head and Neck/ANATOMY:1ac3369a-afb8-4c59-a628-7014069b13bc
|
||||
|
||||
### CNVII (Facial Nerve)
|
||||
Head and Neck/ANATOMY:98cb2d45-e64c-4295-9662-3470cd46513a
|
||||
|
||||
## Cases
|
||||
|
||||
- {'cases': [{'authors': [{'key': '564b28bd-4dbe-4066-9201-d10d689688fb', 'value': 'Christine M. Glastonbury, MBBS'}], 'caseVersionId': '19773c63-084f-4e8a-a6ad-4599b73b6f3f', 'description': 'Typical CECT and MR case of a tubular, cystic parotid schwannoma.\r\n\r\nAxial CECT (#1-3) demonstrates a low-density lesion (open arrows) within the superficial lobe of the parotid, which appears slightly denser than the normal parotid tissue. Sagittal reformatted CECT (#4) best shows extension of the lesion (open arrows) to the stylomastoid foramen (arrow), which appears widened. Axial (#5-7) and coronal (#8-10) T2 MR reveal this lesion (arrows) to be markedly hyperintense and very well circumscribed. T1 MR (#11) shows the mass (arrows) to have similarly well-defined margins and to have homogeneous low signal. It is only on T1 C+ FS MR (#12) that heterogeneous enhancement of this lesion (arrows) reveals to have a cystic internal nature.', 'history': 'Patient presented with a longstanding parotid mass without facial nerve weakness.', 'imagePoolId': '862231cf-68b1-4e58-9b8b-be9063f724a2', 'name': 'Cystic, tubular', 'teachingPoint': None, 'demographics': '36 Years old male'}, {'authors': [{'key': '564b28bd-4dbe-4066-9201-d10d689688fb', 'value': 'Christine M. Glastonbury, MBBS'}], 'caseVersionId': '75347872-f89b-4095-b34c-b96fcca92970', 'description': "Typical MR case of a target-like schwannoma of the parotid.\n\nAxial T1 MR (#1) shows a heterogeneous well-defined solid mass (arrow) in the superficial lobe of the left parotid. On T2 MR (#2,3) the lesion shows central hyperintensity (arrow) with a peripheral intermediate signal rim (curved arrow), and this target-like feature is also seen on the post-contrast images (#4,5) where the tumor's periphery shows greater enhancement (curved arrow).", 'history': 'Patient presented with a slowly growing lump and no evidence of facial nerve abnormality. FNA revealed spindle cells without a clear diagnosis.', 'imagePoolId': '1cf4abc6-531a-4b67-89ab-a7759a83593d', 'name': 'Target-like', 'teachingPoint': None, 'demographics': '38 Years old male'}, {'authors': [{'key': '564b28bd-4dbe-4066-9201-d10d689688fb', 'value': 'Christine M. Glastonbury, MBBS'}], 'caseVersionId': 'b0d85e05-a09b-45ac-8e58-9bdb94bde5f0', 'description': 'Typical case of homogeneous facial nerve schwannoma within the parotid space.\n\nAxial T1 MR (#1) and axial and sagittal T2 MR (#2,3) show a well-defined mass (arrow) in the right parotid, immediately anterior to the mastoid tip. Post-contrast T1 MR (#4) shows homogeneous enhancement of the mass. Notice the lesion "points" into the stylomastoid foramen (open arrow, #2,4). The mastoid segment of the facial nerve can also be followed into the mass on the sagittal view (open arrow, #3).\n\nPearls: The contour of this mass makes it unlikely to be a large lymph node. The sharply defined contour suggests either a benign or low-grade malignant parotid neoplasm, however the intermediate T2 signal intensity is uncommon for benign mixed tumors. Features such as these should raise suspicion for a schwannoma so that the surgeon is able to preoperatively plan for the possibility that this arises from the facial nerve.', 'history': 'This young man presented with a mass and FNA suggested pleomorphic adenoma. His facial nerve function was normal both pre and post-resection.', 'imagePoolId': '813c6ffb-93aa-4802-bea8-550c4144f5e4', 'name': 'Homogeneous', 'teachingPoint': None, 'demographics': '16 Years old male'}], 'caseType': 'typical', 'name': 'TYPICAL'}
|
||||
- {'cases': [{'authors': [{'key': '564b28bd-4dbe-4066-9201-d10d689688fb', 'value': 'Christine M. Glastonbury, MBBS'}], 'caseVersionId': '3ba5eede-00c5-4b9b-b2db-c0a31f1e10a5', 'description': 'Variant MR case of a tubular parotid schwannoma.\r\n\r\nAxial T1 MR (#1-3) demonstrates a subtle, tubular low-density lesion (arrows) within the superficial lobe of the right parotid gland. The lesion is along the expected course of the intraparotid facial nerve, lateral to the retromandibular vein (curved arrow, #1). On axial T2 FS MR (#4-6) images, the mass is readily evident as a heterogeneous, tubular hyperintense lesion (arrows). The lesion (arrows, #7-9) has minimal contrast enhancement on axial T1 C+ FS MR.\r\n\r\nThe initial FNA was hypocellular, but the second attempt revealed schwannoma. The lesion has not been excised.', 'history': 'Patient presented with a palpable mass and right pain in the nasolabial fold and preauricular to right neck; he had but normal facial nerve function.', 'imagePoolId': 'ddeb10e9-3923-4fae-b3fb-cc436361d66f', 'name': 'Tubular', 'teachingPoint': None, 'demographics': '59 Years old male'}], 'caseType': 'variant', 'name': 'VARIANT'}
|
||||
|
||||
|
||||
## Images
|
||||
|
||||
|
||||
### Selected Images
|
||||
|
||||
|
||||
*Axial T2 FS MR shows a heterogeneous, hyperintense parotid mass wedged into the stylomastoid foramen <img src='img/arrows/WS.png'/>. The location & characteristic target sign suggest the possibility of facial schwannoma.*
|
||||
|
||||
|
||||
*Axial T2 FS MR shows a heterogeneous, hyperintense parotid mass wedged into the stylomastoid foramen <img src='img/arrows/WS.png'/>. The location & characteristic target sign suggest the possibility of facial schwannoma.*
|
||||
|
||||
|
||||
*Coronal T1 C+ FS MR in the same patient shows an enhancing schwannoma along the main trunk of the facial nerve with the target sign & small intratumoral cysts <img src='img/arrows/WS.png'/>. An additional clue to the diagnosis is contiguous enhancing tumor along the intratemporal facial nerve <img src='img/arrows/WC.png'/> extending into the IAC <img src='img/arrows/WO.png'/>.*
|
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|
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|
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*Axial CECT in a patient with neurofibromatosis type 2 shows a round, subcentimeter mass <img src='img/arrows/BS.png'/> in the anterior aspect of the superficial parotid lobe. This schwannoma has heterogeneous enhancement but no cystic areas because of its small size.*
|
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|
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|
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*Coronal bone CT shows smooth expansion of the vertical segment of the facial canal <img src='img/arrows/WS.png'/>. The facial nerve schwannoma extends from the parotid gland <img src='img/arrows/WO.png'/> up through the stylomastoid foramen.*
|
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|
||||
|
||||
### Additional Images
|
||||
|
||||
|
||||
*Axial T1 FS MR shows a small mass <img src='img/arrows/WS.png'/> in the superficial lobe of the parotid gland. It has heterogeneous high signal. There are no imaging features that would suggest schwannoma over the far more common benign mixed tumor (BMT).*
|
||||
|
||||
|
||||
*Coronal T1 C+ FS MR shows a tubular mass <img src='img/arrows/WS.png'/> in the inferior superficial parotid lobe. Small schwannomas usually do not have cystic regions. This patient has neurofibromatosis type 2, as evidenced by the schwannoma along CNV3 <img src='img/arrows/WO.png'/>.*
|
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|
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|
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*Coronal T1 C+ FS MR shows an oval, heterogeneously enhancing mass <img src='img/arrows/WS.png'/> with a large intramural cyst <img src='img/arrows/WO.png'/> in the superficial parotid lobe. The imaging appearance is similar to schwannomas in other anatomic locations.*
|
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|
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|
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*Axial T1 C+ MR shows a mass <img src='img/arrows/WS.png'/> with enhancement that allows it to blend into the surrounding high-intensity parotid fat. Fat-saturated images are useful to distinguish intraparotid schwannomas after contrast has been administered.*
|
||||
|
||||
Reference in New Issue
Block a user