Differences in extension patterns between adenoid cystic carcinoma of the nasopharynx and nasopharyngeal carcinoma on MRI

Objective: This study aimed to map differences in extension patterns between adenoid cystic carcinoma (ACC) of the nasopharynxandnasopharyngeal carcinomaon magnetic resonance imaging (MRI) and provide more information for treatments. Methods: MRI examinations and clinical records were reviewed in 18 patients with ACC of the nasopharynx and 182 patients with nasopharyngeal carcinoma (NPC). All patients had biopsy to confirm diagnosis. Differences between NPC and ACC in terms of extension patterns were identified by the retrospective analysis of images from patients undergoing MRI. Results: Patients with ACC of the nasopharynx obtained a higher rate of staging T4 (14.3% vs. 38.9%, P = 0.007) and paralyzed cranial nerves (6.0% vs. 38.9%, P < 0.001). EpsteinBarr (EB) virus infection was not correlated with ACC incidence. No significant difference was observed in invasion to skull base between ACC of the nasopharynx and NPC (53.3% vs. 66.7%, P = 0.277). Involvement of cranial nerve canal (32.4% vs. 55.6%, P = 0.049) and cavernous sinus (13.7% vs. 33.3%, P = 0.028) was more frequently detected by MRI on patients with ACC of the nasopharynx. Lymph node metastasis was infrequently diagnosed in patients with ACC of the nasopharynx. Conclusion: As seen on MRI images, ACC of the nasopharynx is characterized by a high incidence of perineural invasion, frequent and aggressive local infiltration, and infrequently, lymph node metastasis.