statdx/docs_md/articles/skull-base-chondrosarcoma_d52746d2-9761-43a6-8f47-a2ccc01d612d.md

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title	docid	authors	breadcrumbs	category	cmeTopicId	documentVersionId	imageCount	lastUpdated	pageDescription	pageKeywords	pageTitle	enhancedTitle	type	references	breadcrumbs
Skull Base Chondrosarcoma	d52746d2-9761-43a6-8f47-a2ccc01d612d	key value 94f835c8-fa13-4e8a-995b-53048e6b0605 Philip R. Chapman, MD	name slug treeNodeId Head and Neck head-and-neck ed24ed8c-5d57-4629-879b-447b82d2973d name slug treeNodeId Diagnosis diagnosis 19b6b986-97d0-40e7-b317-00f0c5cd8fa2 name slug treeNodeId Skull Base Lesions skull-base-lesions e2f573c9-3c74-435d-86f7-fe1d6c157f65 name slug treeNodeId Diffuse or Multifocal Skull Base Disease diffuse-or-multifocal-skull-base-d- b7ce2ad6-77dc-4c50-a083-5fd04739fa1e name slug treeNodeId Skull Base Chondrosarcoma skull-base-chondrosarcoma null	Head and Neck	2e3b4196-d650-4dad-9cfb-638a0a54444e	b1cf1027-9e19-466e-976d-ea1d55114892	16	08/10/21	Skull Base Chondrosarcoma	Head and Neck, Diagnosis, Skull Base Lesions, Diffuse or Multifocal Skull Base Disease, Skull Base Chondrosarcoma	Skull Base Chondrosarcoma | STATdx	Skull Base Chondrosarcoma	DX	true	Head and Neck Diagnosis Skull Base Lesions Diffuse or Multifocal Skull Base Disease Skull Base Chondrosarcoma

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title: "Skull Base Chondrosarcoma" docid: "d52746d2-9761-43a6-8f47-a2ccc01d612d" authors:

• key: "94f835c8-fa13-4e8a-995b-53048e6b0605" value: "Philip R. Chapman, MD" breadcrumbs:
• name: "Head and Neck" slug: "head-and-neck" treeNodeId: "ed24ed8c-5d57-4629-879b-447b82d2973d"
• name: "Diagnosis" slug: "diagnosis" treeNodeId: "19b6b986-97d0-40e7-b317-00f0c5cd8fa2"
• name: "Skull Base Lesions" slug: "skull-base-lesions" treeNodeId: "e2f573c9-3c74-435d-86f7-fe1d6c157f65"
• name: "Diffuse or Multifocal Skull Base Disease" slug: "diffuse-or-multifocal-skull-base-d-" treeNodeId: "b7ce2ad6-77dc-4c50-a083-5fd04739fa1e"
• name: "Skull Base Chondrosarcoma" slug: "skull-base-chondrosarcoma" treeNodeId: null category: "Head and Neck" cmeTopicId: "2e3b4196-d650-4dad-9cfb-638a0a54444e" documentVersionId: "b1cf1027-9e19-466e-976d-ea1d55114892" imageCount: 16 lastUpdated: "08/10/21" pageDescription: "Skull Base Chondrosarcoma" pageKeywords: "Head and Neck, Diagnosis, Skull Base Lesions, Diffuse or Multifocal Skull Base Disease, Skull Base Chondrosarcoma" pageTitle: "Skull Base Chondrosarcoma | STATdx" enhancedTitle: "Skull Base Chondrosarcoma" type: "DX" references: true breadcrumbs:
• "Head and Neck"
• "Diagnosis"
• "Skull Base Lesions"
• "Diffuse or Multifocal Skull Base Disease"
• "Skull Base Chondrosarcoma"

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KEY FACTS

• Terminology

  • Skull base chondrosarcoma (CSa-SB): Chondroid malignancy of skull base

• Imaging

  • Typical location off-midline, centered onpetrooccipital fissure
  • CT - Characteristic chondroid tumor matrix calcification in 50% - Arc or ring-like calcifications - Sharp, narrow, nonsclerotic transition zone to adjacent normal bone
  • MR - High T2 signal with scattered hypointense foci (calcifications) - Heterogeneously enhancing - Whorls of enhancing lines within tumor matrix often seen

• Top Differential Diagnoses

  • Chordoma
  • Skull base metastasis
  • Plasmacytoma
  • Nasopharyngeal carcinoma (invasive)
  • Meningioma
  • Benign petrous apex lesions

• Clinical Issues

  • Typically, middle-aged patient with insidious onset of headache and cranial nerve palsies (especially CNVI)

• Diagnostic Checklist

  • Is lesion off-midline (CSa) or in midline (chordoma)?
  • Do calcifications represent arc-whorl intralesional calcifications (CSa) or fragmented destroyed bone (chordoma)?
  • Consider MR angiography or CTA for preoperative characterization of vessel involvement

TERMINOLOGY

• Abbreviations

  • Skull base chondrosarcoma (CSa-SB)

• Definitions

  • CSa-SB: Chondroid malignancy of skull base

IMAGING

• General Features

  • Best diagnostic clue

    - Solitary enhancing osteolytic soft tissue mass, centered at petrooccipital fissure (POF) ± chondroid matrix
    

  • Location

    - Off-midline at **POF** (2/3)
    - Anterior basisphenoid (1/3)
    - Rarely multiple
    

  • Size

    - Variable, usually > 3 cm at time of diagnosis
    

  • Morphology

    - Well-circumscribed, lobulated margins
    - Lobulated growth in 3 dimensions results in cauliflower shape
    

• CT Findings

  • NECT

    - Soft tissue component is relatively dense
    

  • CECT

    - Variable, heterogeneous enhancement
    

  • Bone CT

    - Expansile mass at POF producing erosive or destructive bone changes in clivus and petrous apex
    - ~ 50% will have radiographically classic chondroid matrix with **"rings and arcs" calcification**
    - Sharp, narrow, nonsclerotic transition zone to adjacent normal bone
    

• MR Findings

  • T1WI

    - Low to intermediate signal intensity relative to gray matter
            - ↓ signal foci within tumor may suggest underlying coarse matrix mineralization or fibrocartilaginous elements
    

  • T2WI

    - Variable, usually **high signal**
            - CSa-SB may be homogeneously hyperintense or simply contain localized zones of hyperintensity
            - Degree of T2 hyperintensity is inversely related to degree of calcified matrix
            - Steady-state free precession T2 images may be low signal (even if bright on T2 spin echo)
    - Hypointense foci (calcifications) less conspicuous than on CT
    

  • PD/intermediate

    - High signal
    

  • T1WI C+

    - Heterogeneous enhancement
            - Usually has nodular or focal enhancement within tumor
            - Whorls of enhancing lines within tumor matrix often seen
    

• Angiographic Findings

  • Avascular or hypovascular mass
  • Internal carotid artery displacement ± encasement

• Imaging Recommendations

  • Best imaging tool

    - Combination of multiplanar, gadolinium-enhanced MR and high-resolution bone CT
    

  • Protocol advice

    - High-resolution axial bone CT for evaluation of chondroid matrix and pattern of bone destruction
    - MR of skull base to include T2WI and multiplanar T1WI, followed by T1WI C+ FS in same planes for direct comparison
    - MRA and MRV, or CTA helpful to assess vascular involvement preoperatively
            - Carotid injury risk higher for endoscopic resection of CSa-SB
    - Preoperative angiography with test occlusion if vessel sacrifice necessary
    

DIFFERENTIAL DIAGNOSIS

• Chordoma

  • Destructive clival lesion; bone fragments within matrix
  • Midline > lateral location
  • Low T1 and markedly high T2 MR signal; enhancing mass
  • Chondroid chordomas more aggressive and worse prognosis
  • May be impossible to distinguish chordoma from chondrosarcoma on routine imaging

• Skull Base Metastasis

  • Bone CT: Destructive mass that can be anywhere in skull base
  • MR: Often multiple enhancing, invasive lesions
  • Typically low to intermediate T2 signal
  • Known primary tumor

• Plasmacytoma & Multiple Myeloma

  • Usually more midline, within clivus
  • T2 signal is low to intermediate

  • 50% have concurrent multiple myeloma - Multiple lesions of skull base or calvarium generally excludes CSa-SB

• Nasopharyngeal Carcinoma

  • Primary mass in nasopharyngeal mucosal space
  • Tumor invades superiorly to clivus, foramen lacerum, and POF

• Meningioma

  • Calcification in meningioma can mimic chondroid matrix
  • Hyperostosis possible; not typically destructive in absence of invasion
  • Low to intermediate T2 MR signal; enhancing with dural tails
  • Skull base meningioma occurring just above POF with bone invasion could closely resemble chondrosarcoma

• Non-Hodgkin Lymphoma

  • Lymphoproliferative neoplasm with focal or multifocal, osseous &/or extraosseous involvement of skull base
  • Low to intermediate T2 MR signal, may restrict on DWI

• Nonneoplastic Lesion of Petrous Apex

  • Includes benign, expansile lesions: Cholesteatoma, mucocele, cholesterol granuloma - Should be nonenhancing, smoothly marginated without calcified matrix
  • High signal from asymmetric petrous apex marrow can mimic enhancing tumor
  • Petrous apicitis could demonstrate inflammatory enhancement of petrous apex with permeative bone changes - Expect acute clinical syndrome with fever, leukocytosis, Gradenigo syndrome

• Chondromyxoid Fibroma

  • Rare, expansile, noninfiltrating skull base mass
  • Areas of ground-glass density may be seen
  • Appearance may overlap with CSa-SB

PATHOLOGY

• General Features

  • Etiology

    - Arises from remnants of embryonal cartilage, endochondral bone, or from primitive mesenchymal cells in meninges
            - May arise from metaplasia of meningeal fibroblasts
    

  • Genetics

    - May complicate Ollier disease and Maffucci syndrome
    

• Staging, Grading, & Classification

  • Classification - Conventional CSa: Hyaline (7%), myxoid (30%), or mixed (63%) - Clear cell - Mesenchymal - Dedifferentiated
  • Grading from low to high grade - Based on degree of cellularity, pleomorphism, mitoses, and multinucleated cells

• Gross Pathologic & Surgical Features

  • Smooth, lobulated mass "welling up" from POF
  • Cut surface shows gray-white, glistening parenchyma

• Microscopic Features

  • Hypercellular tumor composed of chondrocytes with hyperchromatic, pleomorphic nuclei and prominent nucleoli - Binucleate or multinucleate cells are rule
  • Hyaline matrix may calcify in "ringlets" - Intercellular matrix is solid in hyaline type compared to mucinous/gelatinous matrix in myxoid or mixed types
  • Histology may overlap with or be confused with that of chordoma - Histology particularly confusing in chondroid chordoma, myxoid CSa - Differentiation facilitated by immunohistochemical staining

CLINICAL ISSUES

• Presentation

  • Most common signs/symptoms

    - **Abducens (CNVI) palsy** due to proximity of Dorello canal
    - **Headache**
    - Mean duration of symptoms at diagnosis = 27 months
    

  • Other signs/symptoms

    - Other cranial nerve palsies (CNIII, V, VII, VIII)
    

  • Clinical profile

    - Middle-aged patient with insidious onset of headaches and cranial nerve palsies
    

• Demographics

  • Age

    - Range: 10-80 years
    - Mean: 40 years
    

  • Epidemiology

    - 6% of all skull base tumors
    - 75% of all cranial CSa occur in skull base
    

• Natural History & Prognosis

  • Prognosis depends on extent at diagnosis, histologic grade, and completeness of surgical resection - Disease-specific 10-year survival rates of 99% recently reported - Most central CSa-SBs are well to moderately differentiated - High-grade CSa metastasizes to bones and lung more frequently
  • Conventional CSa: Indolent growth pattern - Most are slow growing, locally invasive, but rarely metastasize
  • Mesenchymal and dedifferentiated forms: Aggressive behavior; poor prognosis

• Treatment

  • Aggressive resection associated with significant morbidity and low likelihood of complete resection - Basal subfrontal approach used for tumor that invades clivus and extends anteriorly into sphenoid and ethmoid sinuses - Subtemporal and preauricular infratemporal approach used when CSa extends laterally beyond petrous internal carotid artery
  • Combined radical resection and postoperative, high-dose, fractionated precision conformal radiation therapy most often utilized - Charged particle radiation therapy (protons or carbon ions) alone or combined with subtotal resection

DIAGNOSTIC CHECKLIST

• Consider

  • Is lesion in off-midline (CSa) vs. midline (chordoma)?
  • Do calcifications represent arc-whorl intralesional calcifications (CSa) or fragmented destroyed bone (chordoma)?
  • Does patient have known primary neoplasm (metastasis), myeloma (plasmacytoma), or nasopharyngeal mass (nasopharyngeal carcinoma)?

• Image Interpretation Pearls

  • Classic appearance: Heterogeneously enhancing tumor located at POF with hyperintense signal on T2 MR - CT shows chondroid mineralization and bone destruction
  • When no tumor matrix found, difficult to tell from CSa plasmacytoma, focal metastasis, or chondromyxoid fibroma

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References

Selected References

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Images

Selected Images

Axial graphic depicts the classic location of a chondrosarcoma of the skull base centered in the left petrooccipital fissure . Note the normal right petrooccipital fissure . Chondroid calcifications, depicted in yellow, are present within the lesion .

Axial graphic depicts the classic location of a chondrosarcoma of the skull base centered in the left petrooccipital fissure . Note the normal right petrooccipital fissure . Chondroid calcifications, depicted in yellow, are present within the lesion .

Axial T2 MR reveals a large, high-signal chondrosarcoma of the left petrooccipital fissure. Note that the vertical segment of the petrous internal carotid artery is compressed . Note the normal right petrooccipital fissure .

Axial T1 C+ MR shows mottled enhancement within a chondrosarcoma centered at the left petrooccipital fissure. Calcified matrix is seen as a focal low signal intensity area within the otherwise enhancing tumor. The left internal carotid artery is patent .

Axial bone CT demonstrates typical chondroid calcification in a left petrooccipital fissure chondrosarcoma. In this case, no significant destruction of the adjacent petrous apex is appreciated.

Axial bone CT shows rounded and arc-like calcified foci in this large chondrosarcoma centered at the petrooccipital fissure. Up to 50% of chondrosarcomas demonstrate matrix calcification. Note slight narrowing of the left vidian canal .

Axial bone window CT shows subtle bone destruction with cortical erosion in this small left petrous apex chondrosarcoma. No calcified matrix is seen. MR showed a corresponding T2-hyperintense and enhancing mass in this location.

Axial T2 MR shows a hyperintense chondrosarcoma involving the right petrous apex and extending into the right cerebellopontine angle cistern (CPA) . The petrous carotid artery is displaced anteriorly .

Axial T1 C+ FS MR demonstrates avid enhancement in this chondrosarcoma. Note petrous apex and CPA cistern involvement. Most skull base chondrosarcomas emanate from the petrooccipital fissure. However, when they become large, it may be hard to see the point of origin.

Axial T2 MR shows a hyperintense right parasellar chondrosarcoma that extends into the prepontine cistern and sphenoid sinus . Note internal carotid and basilar arterial displacement by the mass.

Axial T1 C+ FS MR shows moderate enhancement within a right parasellar chondrosarcoma . The patient presented with intractable headache, epistaxis, and diplopia. Tumor invades prepontine cistern and sphenoid sinus , partly encases the right ICA , and displaces the basilar artery .

Additional Images

Axial bone CT of the skull base shows a chondrosarcoma centered over the left petrooccipital fissure. Notice the absence of chondroid calcifications within the tumor matrix in this case.

Axial bone CT in a patient with a petro-occipital chondrosarcoma shows coarse chondroid calcifications within the tumor matrix .

Axial T2 FS MR shows intermediate, heterogeneous signal in the cephalad margin of a petrooccipital fissure chondrosarcoma . Curvilinear and punctate hypointensities in the lesion are due to chondroid calcifications.

Axial T2 MR shows a hyperintense small early left petrous apex chondrosarcoma . Although one might consider trapped fluid in a pneumatized petrous apex based on the T2 image, associated enhancement and bone destruction on CT suggested a more aggressive process. The cisternal 6th cranial nerves are faintly seen, and their proximity to the petrous temporal bone illustrates why chondrosarcomas here frequently present with 6th nerve involvement.

Axial CECT demonstrates a left cavernous sinus/paracavernous myxoid chondrosarcoma . Orbital apex involvement is present . Note absence of chondroid calcifications.

Axial T2 FS MR in the same patient reveals a homogeneously hyperintense left cavernous and paracavernous myxoid chondrosarcoma . Notice that the cavernous internal carotid artery is nearly surrounded by tumor.