Inverted Papilloma (IP)

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  • IPs (a subtype of Schneiderian Papillomas) are benign, locally aggressive lesions composed of pseudostratified respiratory epithelium that account for 0.4-4% of nasal cavity masses
  • They typically originate from the lateral wall of the nasal cavity, although they may also arise from the paranasal sinuses, and grow inward and into the underlying bone
  • IPs are often resected, as up to 10% undergo malignant transformation, most commonly into squamous cell carcinoma 
  • The rate of recurrence after resection is between 2 and 15%
  • Imaging is insufficiently specific to reliably differentiate an IP from other benign (inflammatory or antrochoanal polyps) and malignant (sinonasal carcinoma) masses 
  • On CT, IPs appear as an enhancing nasal or sinus mass, which may widen the maxillary infundibulum; identification of a hyperostotic stalk favors IP over other sinonasal masses and can help direct the surgical approach
  • On MRI, IPs classically demonstrate a “cerebriform” or “brainlike” appearance, seen as heterogeneous alternating hypointense and hyperintense bands on T2-weighted and contrast-enhanced T1-weighted images
  • Classic features on CT (hyperostotic stalk) and MRI (cerebriform T2 signal) favor the diagnosis of IP
  1. Chawla A, Shenoy J, Chokkappan K, Chung R. Imaging features of sinonasal inverted papilloma: a pictorial review. Current Problems in Diagnostic Radiology 2016; 45(5):347-53
  2. Ojiri H, Ujita M, Tada S, Fukuda K. Potentially distinctive features of sinonasal inverted papilloma on MR imaging. American Journal of Roentgenology 2000; 175:465-468

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