Case of the Week

Background:

• Sinonasal squamous cell carcinoma (SNSCC) is a very rare cause of clival mass, with clival masses only accounting for 0.1–0.5% of all intracranial tumors, and sinonasal primary malignancies only making up 3–5% of all head and neck cancers.
• The most common clival mass is a chordoma—representing 40% of all clival lesions—with chondrosarcoma being the second most common tumor.
• Predictors of poor prognosis include poor cellular differentiation, paranasal sinus origin, and pterygopalatine involvement.

Clinical Presentation:

• Clival pathologies can present as asymptomatic incidental imaging findings or with nonspecific symptoms such as headaches, cranial nerve palsies, and visual disturbances.

Key Diagnostic Features:

• On CT, SNSCC characteristically appears as an expansile mass with aggressive bony destruction to the sinus walls and surrounding structures. Larger lesions tend to have a necrotic center.
• On MRI, SNSCC demonstrates T1 isointensity, T2 mild hyperintensity, and moderate enhancement. Smaller lesions demonstrate homogeneous enhancement while the larger tumors are usually more heterogeneous with areas of necrosis and hemorrhage.

Differential Diagnoses:

• Chordoma: commonly midline. On CT, chordoma appears as a well-circumscribed, expansile–soft tissue mass with osseous destruction and occasional irregular intratumoral calcifications. On MRI, it demonstrates T1 iso-hypointense signal and very high T2 signal intensity. Heterogeneous enhancement with a honeycomb appearance has also been noted.
• Chondrosarcoma: commonly off midline. On CT, chondrosarcoma appears as a soft tissue mass with occasional ring and arc calcifications due to chondroid matrix formation. On MRI, it demonstrates T1 hypointense signal, T2 hyperintense signal, and susceptibility artifact on SWI/gradient recalled-echo imaging, secondary to calcifications, and shows heterogeneous enhancement on postcontrast imaging.

Treatment:

• Endoscopic surgical resection with postoperative radiotherapy appears to be the optimal approach. 
• There has been an improvement in therapy with precision radiotherapy and induction chemotherapy.