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Sinonasal squamous cell carcinoma

Sinonasal squamous cell carcinoma is the most common sinonasal malignancy, typically presenting in older males (>50 years) with delayed diagnosis due to nonspecific symptoms like nasal obstruction, facial pain, rhinorrhea, and epistaxis. Imaging is essential for local staging, surgical planning, and detection of metastases.

Key Images

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Look For First
  • Irregular heterogeneous soft-tissue mass with adjacent bone destruction in maxillary sinus, nasal cavity, or ethmoid sinuses
  • On MRI: variable T1/T2 signal intensity with heterogeneous enhancement pattern; necrotic centers in larger lesions
  • Invasion into adjacent spaces (orbit, skull base, intracranial) and perineural spread best assessed on MRI
  • FDG avidity on PET-CT indicating metabolically active tumor
Key Image Findings
  • CT shows irregular heterogeneous soft-tissue density mass with variable enhancement; larger tumors demonstrate areas of necrosis with heterogeneous rather than homogeneous enhancement patterns.
  • MRI T1 signal is typically isointense to hypointense relative to muscle, with potential hyperintense areas if hemorrhage is present within the tumor.
  • MRI T2 signal is variable and typically moderately hyperintense, with greater hyperintensity in necrotic regions; this T2 hyperintensity helps distinguish necrosis from trapped secretions.
  • T1 post-gadolinium enhancement varies based on tumor size: smaller lesions without necrosis show moderate homogeneous enhancement, while larger necrotic lesions demonstrate heterogeneous enhancement.
  • Bone destruction adjacent to the mass is a key aggressive feature, reflecting invasion through the cortex and medullary bone.
  • MRI is superior to CT for assessing invasion into adjacent spaces including the orbit, facial skeleton, skull base, and intracranial compartments.
  • Perineural spread may be present along cranial nerves (particularly CN V) and is better detected on MRI with dedicated imaging.
  • PET-CT demonstrates significant FDG avidity in sinonasal squamous cell carcinomas and their metastases, useful for staging and detecting nodal involvement and distant disease.
Differential Diagnosis
  • [
  • "Sinonasal adenocarcinoma: typically arises from mucous glands and has different histology; keratinizing SCC lacks mucin-producing features.",
  • "Olfactory neuroblastoma: arises at cribriform plate, has different age presentation (younger), and distinct neural differentiation on pathology; imaging shows more columnar location at skull base.",
  • "Sinonasal lymphoma: typically homogeneous soft-tissue attenuation on CT without prominent bone destruction; shows different enhancement patterns and lacks necrosis.",
  • "Sinonasal mucosal melanoma: pigmentation may occasionally be appreciated on imaging; has different histopathology with melanin and different clinical behavior.",
  • "Chronic invasive fungal sinusitis: demonstrates different imaging characteristics with hypodensity and calcification patterns; may lack obvious mass formation and has different clinical presentation.",
  • "Juvenile nasopharyngeal angiofibroma: occurs in younger patients, demonstrates vascular flow voids on MRI, and arises from nasopharyngeal region with characteristic "waisting" at sphenopalatine foramen."
  • ]
Discussion

Keratinizing squamous cell carcinomas are associated with smoking and environmental/occupational carcinogens (wood/leather particles, nickel, chrome, arsenic, formaldehyde); non-keratinizing tumors are increasingly linked to high-risk HPV infection with better prognosis.

The maxillary sinus is the most common primary site (>50% of cases), followed by nasal cavity and ethmoid sinuses; sphenoid and frontal sinus involvement is rare but carries worse prognosis (5-year survival <30%).

HPV-positive tumors have improved survival (~75%) due to more frequent nasal cavity location enabling earlier diagnosis with less extensive local invasion compared to maxillary tumors (~35% survival).

Clinical presentation is nonspecific and delayed; symptoms depend on tumor extension direction—anterior growth causes facial swelling, orbital invasion causes proptosis/visual disturbance, posterior/skull base invasion causes neurological symptoms.

Microscopic appearance differs: keratinizing SCC shows infiltrative nests with prominent keratinization and desmoplasia, while non-keratinizing SCC shows expansile lobules of high nuclear-to-cytoplasmic ratio cells with minimal desmoplasia and smooth borders.

Cross-sectional imaging (CT and MRI) is complementary: CT excels at assessing bone destruction; MRI is superior for soft-tissue invasion, perineural spread, and distinguishing tumor from trapped secretions and determining extent of intracranial involvement.

Reporting Pearls

When describing sinonasal SCC, specify the primary site (maxillary sinus, nasal cavity, ethmoid), document the presence and extent of adjacent bony destruction, characterize the enhancement pattern (homogeneous in small lesions vs. heterogeneous with necrosis in larger masses), clearly delineate invasion into the orbit, skull base, intracranial space, and nasopharynx, and assess for perineural spread along CN V to guide surgical planning.

Pitfalls
  • Confusing tumor necrosis with trapped secretions: MRI with T2 signal and post-contrast enhancement helps distinguish—necrotic tumor shows rim enhancement around nonenhancing center, while secretions do not enhance.
  • Underestimating extent of invasion: smaller tumors on CT may appear well-demarcated, but MRI reveals subtle invasion into adjacent soft tissues and potential perineural spread requiring higher surgical margins.
  • Missing intracranial or orbital involvement on CT alone: MRI is more sensitive and should always be performed to fully stage tumors and guide surgical approach, particularly for anterosuperior masses.
  • Assuming imaging diagnosis: squamous cell carcinoma cannot be definitively diagnosed on imaging alone; similar appearances occur with adenocarcinoma, lymphoma, and other sinonasal malignancies—tissue confirmation is mandatory.
Source: Reference source

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