The CT and MRI observations of small cell neuroendocrine carcinoma in paranasal sinuses

Primary small cell neuroendocrine carcinoma (SNEC) of paranasal sinuses is an extremely rare malignant tumor known for its aggressive clinical behavior.

Nineteen patients with SNEC in paranasal sinuses by magnetic resonance imaging (MRI) (n = 19) and computerized tomography (CT) and MRI (n = 18) were retrospectively studied. CT and MRI were undertaken to investigate tumor features.

The lesions were located in the ethmoidal sinus (n = 6), maxillary sinus (n = 4), and bilateral sphenoid sinus (n = 9). All lesions showed a symmetry or ‘pigeon’ pattern in the bilateral sphenoid sinus (n = 9). On CT scan, the lesions showed to be isodense (n = 3) or mild hyper-dense (n = 15). Bone changes included bony absorption or sclerosis (n = 3) and moth-eaten bone destruction (n = 16). Mild cystic components were visible in five patients with SNEC. There was no evidence of calcification in any of the SNEC tumors. The lesions were isointense on T₁WI and isointense (n = 6) or mild hyper-intense on T₂WI (n = 13). The lesions showed mild or moderate homogeneous enhancement after the administration of a contrast agent. The aggressive nature of the tumors was demonstrated by invasion of adjacent structures, which showed involvement of the nasal cavity (n = 17), orbits (n = 15), pterygopalatine fossa (n = 9), ethmoidal sinus and sphenoid (n = 5), clivus ossis occipitalis (n = 2), cavernous sinus and internal carotid canal (n = 5), optic canal (n = 3), jugular fossa (n = 2), anterior fossa (n = 2), apex partis petrosae ossis temporalis (n = 3), meninges (n = 2), temporal fossa and infratemporal fossa (n = 4), and pharyngonasal cavity and parapharyngeal space (n = 3). There was evidence of distant metastasis in five (lung) and one (liver) of the tumors. Fifteen patients (15/19, 78.9%) expired within 5 years of the initial diagnosis, and the other patients are currently still alive.

A tumor exhibiting mild or moderate homogeneous enhancement together with a symmetry or ‘pigeon’ pattern in the bilateral ethmoidal sinus may be considered as specific MRI features.