Revisitation of imaging features of skull base chondrosarcoma in comparison to chordoma.

Purpose: Pre-surgical diagnosis of skull base chondrosarcoma (SBC) is often challenging due to the resemblance to chordoma. The goal of this study was to develop an optimal method for predicting SBC diagnosis.

Methods: This retrospective study included patients with histologically diagnosed SBC and skull base chordoma. Their clinical and radiologic features were compared, and the predictive factors of SBC were examined.

Results: Forty-one patients with SBC and 41 with chordoma were included. Most SBCs exhibited hypointensity (25, 64.1%) or isointensity (12, 30.8%) on T1-weighted images, and hyperintensity (34, 87.1%) or mixed intensity (5, 12.8%) on T2-weighted images. MRI contrast enhancement was usually avid or fair (89.7%) with "arabesque"-like pattern (41.0%). The lateral/paramidline location was more common in SBC than in chordoma (85.4% vs. 9.8%; P < 0.01), while midline SBCs (14.6%) were also possible. Multivariate analysis demonstrated that higher apparent diffusion coefficient (ADC) value (unit odds ratio 1.01; 95% confidence interval 1.00-1.02; P < 0.01) was associated with an SBC diagnosis. An ADC value of ≥ 1750 × 10 mm/s demonstrated a strong association with an SBC diagnosis (odds ratio 5.89 × 10; 95% confidence interval 51.0-6.80 × 10; P < 0.01) and yielded a sensitivity of 93.9%, specificity of 97.4%, positive predictive value of 96.9%, and negative predictive value of 95.0%.

Conclusion: The ADC-based method is helpful in distinguishing SBC from chordoma and readily applicable in clinical practice. The prediction accuracy increases when other characteristics of SBC, such as non-midline location and arabesque-like enhancement, are considered together.