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Page 18 of 25 Singh et al. Mini-invasive Surg. 2025;9:28 https://dx.doi.org/10.20517/2574-1225.2024.75

[42]
weighted images . They generally demonstrate avid contrast enhancement and moderately restricted
[42]
diffusion [Figure 26] .
SNEC
SNEC is a rare, highly aggressive malignancy with a high risk of recurrence. It shares a common site of
[43]
origin with SNUC, particularly in the ethmoid sinuses . SNEC most commonly occurs in patients in their
[44]
fifth or sixth decade of life .
On CT, the tumors may appear isodense or mildly hyperdense and typically show avid contrast
enhancement. On MRI, they usually present with ill-defined borders [43,44] . Characteristically, they
demonstrate an isointense signal on T1-weighted images and an isointense to mildly hyperintense signal on
T2-weighted images, with mild to moderate contrast enhancement [43,44] .

SNEC frequently exhibits aggressive invasion beyond the paranasal sinuses, involving the nasal cavity,
[44]
[43]
orbits, superior/inferior orbital fissures, PPF, and optic canal . Bony erosion is also commonly observed .
SINONASAL MUCOSAL MELANOMA
Sinonasal malignant melanoma (SMM) is a rare and highly metastatic tumor, accounting for approximately
1% of all malignant melanomas . Most cases originate in the nasal cavity, with the nasal septum being the
[45]
most common site, followed by the lateral nasal wall. Less frequently, tumors arise in the maxillary sinus or
ethmoid air cells. At the time of diagnosis, up to 40% of cases present with nodal metastases [16,46] .

The imaging characteristics of SMM often do not correlate with its biological aggressiveness, as even
aggressive tumors may appear well-defined and noninvasive on scans. On CT, the appearance is typically
nonspecific, as bony destruction is a common finding in many malignant tumors . On MRI, SMM usually
[16]
appears hyperintense on T1-weighted and hypointense on T2-weighted images, reflecting hemorrhage and
the paramagnetic effects of metal ions bound to melanin [Figure 27] [3,47] . However, intermediate signal
intensity is also frequently observed across MRI sequences. In addition, SMM has the potential for
perineural spread, which may be associated with a prolonged latency period [16,46] .

SINONASAL LYMPHOMA
The head and neck region is the second most common site of extranodal lymphoma after the
gastrointestinal tract. Fewer than 10% of head and neck lymphomas occur in the sinonasal cavity . Nearly
[48]
all sinonasal tract lymphomas are non-Hodgkin lymphomas and can be further divided into B cell, T cell/
[17]
natural killer (NK) cell, or T cell/NK precursor cell subtypes . These tumors typically appear as bulky soft-
[48]
tissue masses in the maxillary sinuses or nasal cavity, often associated with necrosis and invasion of adjacent
soft tissues and bony structures [16,48] .

In Western populations, Epstein-Barr virus (EBV)-negative diffuse large B cell lymphoma is the more
common subtype of sinonasal lymphoma [16,48] . In contrast, EBV-positive T/NK-cell lymphomas are more
[48]
frequently observed in East Asian and South American populations . On CT imaging, sinonasal
lymphomas usually appear as nonspecific, bulky, ill-defined soft-tissue masses with associated bony
[16]
destruction and extension into surrounding soft tissues . On MRI, these tumors often demonstrate
heterogeneous intermediate signal intensity on T1- and T2-weighted images, with moderate enhancement
and restricted diffusion [Figure 28] [16,48] .