Purpose The purpose of this study was to explore the characteristic computed tomography (CT) and magnetic resonance (MR) features of small cell neuroendocrine carcinoma (SNEC) of paranasal sinuses. Materials and Methods Computed tomography (n = 8) and MR (n = 14) images and clinical findings from 14 patients with SNEC of paranasal sinuses were retrospectively reviewed. Results Eight lesions were located in the ethmoidal sinus, 4 in the maxillary sinus, and 2 in the sphenoid sinus. Small cell neuroendocrine carcinoma of the sphenoid sinus showed bilateral asymmetry patterns. On CT images, bony changes were visible in all 8 cases. On MR, 4 cases contained hemorrhage, and 10 cases contained cystic or necrotic areas. All cases demonstrated marked heterogeneous enhancement, with half showing a “cribriform-like” or “geographic” appearance. The nasal cavity was the most common site invaded by SNEC of paranasal sinuses, followed by the orbits. A time-signal intensity curve examination showed a washout-type pattern in all but 1 case. The mean ± SD apparent diffusion coefficient value was 0.702 ± 0.112 (×10 −3 mm 2 /s). According to the Dulguerov staging system, 9 tumors were staged as N0 (1 T1, 1 T2, 5 T3, and 2 T4). The recurrence rate was 64.3%. Conclusions Some characteristics of radiological findings can provide important clues for preoperative diagnosis.

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