Chordoma is a rare, low-grade malignant bone tumor arising from notochord remnants. The sacrum (50-60%) and clivus (25-35%) are the most common locations — both in the midline of the axial skeleton. Very bright T2 signal, lobulated bone destruction ('thumb-like' lobulations), and slow growth are characteristic. Locally aggressive behavior, high recurrence rate, and relative resistance to radiotherapy are important clinical features.
Age Range
40-70
Peak Age
55
Gender
Male predominant
Prevalence
Rare
Chordoma develops from remnant cells of the notochord, which defines the axial skeleton during embryonic development. The notochord normally regresses from the 7th week of gestation, but small remnants (ecchordal remnants or benign notochordal cell tumors) may persist in the sacrum, coccyx, and clivus regions — these remnants can transform into chordoma. Tumor cells contain abundant mucin and glycogen (physaliferous cells); this intracellular vacuolated structure produces very bright signal on T2-weighted MRI because high water-content mucin prolongs T2 relaxation time. The tumor grows slowly but locally aggressively, creating bone destruction with 'thumb-like' lobulated soft tissue mass — these lobulations reflect tumor extension along fascial planes. Chordomas express the brachyury (T) transcription factor, which is a diagnostic marker in immunohistochemistry.
Thumb/finger-like lobulated extensions of chordoma's soft tissue component on T2-weighted series. These lobulations reflect tumor growth along fascial planes and are quite specific for chordoma. In sacral chordoma, lobulated extension into the anterior presacral space, and in clival chordoma into the retropharyngeal/prepontine space, is typical.
On T2-weighted series, chordoma demonstrates very bright (hyperintense) signal — comparable to cerebrospinal fluid (CSF) level high T2 signal. Fibrous septa within the tumor show low signal, creating a lobulated internal structure. 'Thumb-like' lobulations — finger-like tumor extensions — are best evaluated on T2. Hemorrhage and calcification areas appear as focal low signal foci.
Report Sentence
On T2-weighted series, a midline mass in the sacrum demonstrating very bright signal isointense to CSF with lobulated contours is identified, consistent with chordoma.
On T1-weighted series, chordoma demonstrates low to intermediate signal. Mucinous component produces low T1 signal, while intratumoral hemorrhage or proteinaceous content can create focal T1 hyperintensity. Intratumoral fibrous septa and calcifications show low T1 signal. The degree of heterogeneity may reflect the differentiation level of the tumor.
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On T1-weighted series, the sacral mass demonstrates low to intermediate signal intensity with focal high signal areas consistent with intratumoral hemorrhage.
On CT, midline bone destruction in the sacrum or clivus is observed. Amorphous calcifications or destroyed bone fragments within the tumor are characteristic (30-70% of cases). Soft tissue mass extends beyond bone margins in a lobulated fashion. In sacral chordoma, destruction of sacral foramina and anterior soft tissue mass are typical.
Report Sentence
On CT, a midline destructive mass in the sacrum is identified with intratumoral calcifications and anterior lobulated soft tissue extension.
On post-contrast T1 series, chordoma demonstrates heterogeneous enhancement. Fibrous septa and tumor periphery enhance while mucinous areas do not — creating a 'honeycomb' enhancement pattern. The degree of enhancement depends on the solid/mucinous component ratio of the tumor. Dedifferentiated chordoma shows more diffuse and intense enhancement.
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On fat-suppressed post-contrast series, the mass demonstrates heterogeneous honeycomb-pattern enhancement with non-enhancing mucinous areas and enhancing fibrous septa.
On DWI, chordomas show variable diffusion pattern. Classic physaliferous type generally shows high ADC values (>1.5 × 10⁻³ mm²/s) due to high water content. Dedifferentiated chordoma shows lower ADC values (<1.0 × 10⁻³ mm²/s) due to increased cellularity. ADC values are used in predicting histological subtype and monitoring treatment response.
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On DWI, the mass shows bright signal due to T2 shine-through effect, with high ADC values (>1.5 × 10⁻³ mm²/s) on ADC map consistent with mucinous content.
On STIR sequence, fat suppression makes the mucinous component of chordoma even more conspicuous — very bright homogeneous signal. The tumor's relationship with surrounding structures (sacral nerve roots, rectum, bladder) is clearly assessed on STIR. Peritumoral edema and adjacent bone marrow infiltration are best seen on STIR.
Report Sentence
On STIR sequence, the sacral mass demonstrates very bright homogeneous signal, with clear assessment of anterior and posterior soft tissue extension and sacral nerve root relationship.
Criteria
Most common type (90%), physaliferous cells (vacuolated cytoplasm), low mitotic activity, brachyury (+), CK (+), EMA (+)
Distinct Features
Very bright T2 signal (mucin-rich), slow growth, high local recurrence but metastasis rare (5-10%). Honeycomb enhancement pattern on MRI is most typical in this subtype.
Criteria
Contains chondroid matrix areas (cartilage-like), typically clivus location, better prognosis, brachyury (+), S-100 (+)
Distinct Features
CT may show arc-ring calcifications in chondroid matrix areas (similar to cartilage tumors). On MRI, may show more heterogeneous T2 signal than classic type. Distinguished from chondrosarcoma by brachyury positivity. 5-year survival better than classic type.
Criteria
High-grade sarcoma component (fibrosarcoma/undifferentiated pleomorphic sarcoma) + classic chordoma areas, aggressive clinical course, early metastasis, very poor prognosis
Distinct Features
On MRI, lower T2 signal (less mucin, more cellularity), marked restricted diffusion on DWI (ADC <1.0), more intense and diffuse enhancement. Rapid growth and early pulmonary metastasis. Median survival ~12 months. Resistance to radiotherapy more pronounced.
Distinguishing Feature
Chondrosarcoma also shows bright T2 signal but 'arc-ring' calcification pattern is more prominent. Chondrosarcoma is not confined to midline and can show lateral location. On immunohistochemistry, chondrosarcoma is brachyury negative — this is the most important distinguishing marker.
Distinguishing Feature
Giant cell tumor may show eccentric location in the sacrum without midline restriction. Not as bright as chordoma on T2 (lower signal due to hemosiderin component). No intratumoral calcification on CT (unlike chordoma). Brachyury is negative in giant cell tumor.
Distinguishing Feature
Metastases are typically multiple and bilateral without midline restriction. The characteristic lobulated soft tissue mass of chordoma is not seen in metastasis. Metastases are not as bright as chordoma on T2. Known primary malignancy history and multiple foci on PET-CT favor metastasis.
Distinguishing Feature
Sacral schwannoma grows expanding the neural foramen ('dumbbell' shape). May be bright on T2 but bone destruction is not as prominent as chordoma. No intratumoral calcification. 'Target sign' (peripheral high, central low T2 signal) may be seen in schwannoma. S-100 positive, brachyury negative.
Urgency
semi-urgentManagement
En-bloc geniş rezeksiyon altın standarttır (R0 rezeksiyon sağkalımı belirgin artırır). Proton/karbon iyon radyoterapisi inoperabl veya R1/R2 rezeksiyon sonrası önerilir (foton radyoterapisinden daha etkili). Hedefe yönelik tedaviler (imatinib, erlotinib, afatinib) araştırma aşamasında.Biopsy
NeededFollow-up
6-12 aylık MRG ile lokal rekürrens taraması (5 yıldan uzun süre). Akciğer BT ile uzak metastaz takibi. 10 yıllık lokal rekürrens oranı %50-70.Chordoma diagnosis is made by imaging + biopsy. Brachyury (T transcription factor) positivity on immunohistochemistry is diagnostic and distinguishes from chondrosarcoma. For surgical planning, nerve root involvement, vascular relationship, and surrounding organ invasion should be detailed on MRI. In sacral chordoma, urinary and rectal function can be preserved in resection below S3, while risk of neurological deficit is high in resection above S2.
Chordoma is slow-growing but locally aggressive with high recurrence rate. En-bloc surgical resection (wide negative margins) is the gold standard. Conventional radiotherapy has limited efficacy; proton/carbon ion therapy is more effective. Metastasis may occur late (5-40%). 5-year survival is 50-70%.