Radiologic Features for Differentiating Sinonasal Inverted Papilloma and Squamous Cell Carcinoma Arising From Inverted Papilloma Without Bone Destruction.

BACKGROUND AND

OBJECTIVES

Differentiating inverted papilloma (IP) from squamous cell carcinoma arising in IP (IP+SCC) is challenging when computed tomography (CT) demonstrates no bone destruction. This study aimed to identify CT and magnetic resonance imaging (MRI) features that distinguish IP from IP+SCC in cases without bone destruction on CT.

METHODS

We retrospectively reviewed 30 patients with histologically confirmed sinonasal IP (n=15) or IP+SCC (n=15) who underwent preoperative CT and MRI between 2010 and 2023. Imaging variables assessed included tumor origin, tumor volume, CT enhancement pattern, signal intensity on T2-weighted and contrast-enhanced T1-weighted images, apparent diffusion coefficient (ADC), and the presence or loss of the convoluted cerebriform pattern (CCP). Group differences were analyzed using appropriate statistical tests, with p<0.05 considered statistically significant.

RESULTS

There was no statistically significant difference in tumor origin between the IP and IP+SCC groups. Tumor volume and CT enhancement patterns also did not differ significantly between the groups. On MRI, IP+SCC more frequently demonstrated intermediate signal intensity on both T2-weighted and contrast-enhanced T1-weighted images compared with IP (p=0.025 and p=0.029, respectively). Median ADC values were significantly lower in the IP+SCC group than in the IP group (0.99×10-3 vs. 1.20×10-3 mm2/s; p=0.026). Loss of the CCP was more common in the IP+SCC group, although the difference did not reach statistical significance.

CONCLUSION

In sinonasal IP without bone destruction on CT, MRI appears to be more informative than CT for distinguishing IP+SCC from IP. Intermediate signal intensity on T2-weighted and contrast-enhanced T1-weighted images, along with lower ADC values, supports malignant transformation, whereas tumor size, CT enhancement, and CCP alone are less reliable discriminators.