Chondrosarcoma of the skull base is a rare tumor, making up only 7% of head and neck cancers. They most commonly occur at the petro-occipital synchondrosis. CT and MRI are used to identify the characteristic ring and arc calcifications within an expansile, lobulated mass centered off the midline. Differential diagnoses include chordoma, meningioma, metastases and pituitary adenoma. Treatment involves radical resection with a multidisciplinary approach.

1. Chondrosarcoma
of skull Base
Dr.Santosh Atreya
Phase-B Resident
Department of Radiology & Imaging
BSMMU,Dhaka

2. Introduction
• Chondrosarcoma of the skull base are rare
tumors.
• The incidence is reported to be 0.03 per
100,000 persons in the United States

3. Epidemiology
• Chondrosarcomas of the base of the
skull make up only a small fraction of
all chondrosarcomas
• Head and neck chondrosarcomas- only 7%.

4. • Petro-occipital synchondrosis (most common)
• Sphenoethmoidal junction
• Sella turcica
• The majority of chondrosarcomas of the base of the
skull are located off the midline
• Chordomas-usually midline.
Location

6. • The petro-occipital synchondrosis, also known
as the petroclival synchondrosis, is a primary
cartilaginous joint between the basilar part of
the occipital bone and the petrous temporal
bone.
• 'Fissure' and 'junction' are other terms used to
describe this structure,
however, synchondrosis is technically more
correct.

7. Risk factors
• The vast majority –sporadic
• However, some predisposing conditions are
reported, and include:
• previous trauma/fractures

8. Clinical presentation
• Patients usually present due to mass effect,
either on adjacent brain, brainstem, cranial
nerves or (if extension inferiorly) structures of
the superior neck.

9. Chondrosarcoma
• Skull:Painless expanding mass
Types:
• Myxoid (Low grade)-Most common
• Dedifferentiated
• mesenchymal

10. Radiographic features
• Plain radiograph
• Only of historical interest,
• Lytic lesions in 50% and
calcifications in
approximately 60%.
• Differentiation of
chondrosarcomas from
other skull base tumors
was very difficult prior to
cross-sectional imaging.

11. CT
• Thin triplanar bone
algorithm images is
important is confirming
bony involvement and
demonstrating
calcification of the tumor,
often in
characteristic rings and
arcs (70%)
• Centered off mid-line
• Petro-occipital fissure

12. MRI
• T1: low signal
• T2: high signal
• T1 C+ (Gd)
– usually heterogeneous
enhancement
– Scalloped well
circumscribed margin.

13. Chondrosarcoma of the sphenoid in a 56-year-old man. (A) Axial, T2-weighted
MR image shows a lobulated mass at the sphenoid . The mass contains abundant
intermediate signals but also includes hyperintense foci. (B) Axial, contrast-
enhanced, MR image with fat suppression shows peripheral enhancement that
indicates chondrogenic tumor. A pathological analysis revealed grade 1
chondrosarcoma.

14. Differential Diagnosis
• Chordoma
– usually midline projecting posteriorly
• Meningioma
– usually not high T2 signal
– calcification pattern usually not chondroid
• Metastases
– calcification not as common
– more destructive
• Nasopharyngeal carcinoma
– calcification uncommon
– epicentre in the nasopharynx
• Pituitary macroadenoma
– calcification uncommon
– centred on pituitary fossa
• Cavernous sinus hemangioma
– also high T2 signal but usually homogeneous
– no calcification

15. Chordoma
Found in mid-line
Most common-
Sacrococcygeal
30-50%

16. Treatment
• Multidisciplinary approach should be
implemented in managing this rare tumour
apart from radical resection as its mainstay
treatment.

17. Take Away Messages for Radiology
Resident
• Skull base chondrosarcoma typically forms an
expansile mass with multilobulated margins. CT
shows an osteolytic mass. Typical ring and arc
calcification can be seen
• The tumor demonstrates iso- to hypointensity on
non-contrast T1-weighted and hyperintensity on
T2-weighted MR images.
• The contrast enhancement pattern is
heterogeneous with a predominance at the
periphery.