Abstract
Sinonasal inverted papilloma (IP) is a rare benign tumor of the nasal cavity and paranasal sinuses. An IP can be destructive: bone-remodeling tends to recur after surgical resection and it has a significant malignant potential. IP is also associated with squamous cell carcinoma (SCC). However, it is difficult to diagnose an associated malignancy before treatment as the pathological findings are different depending on the sampling site. We retrospectively reviewed 3 patients with SCC arising from IP to analyze predictors of associated malignancy. The chief complaints of two cases included diplopia, headache, trismus and facial nerve palsy. Although these symptoms are suspected for a malignant process, the main complaint of the third case was lateral nasal obstruction alone. Thus, clinical symptoms cannot rule out coexisting malignancy in IP. All three cases had bone destruction on CT. Malignant tumors were diagnosed by biopsy from the bone destruction sites. The characteristic finding on CT, namely bone destruction, which was classified as T4 on the Krouse staging system, was useful to detect the associated malignancy. A convoluted cerebriform pattern (CCP) on MRI is regularly seen in IP. IP with SCC has been reported to show areas of focal loss of a CCP (partial CCP). All of our cases lacked such CCP findings on MRI. Partial CCP or loss of CCP could indicate an associated malignancy in IP. These characteristic findings on CT and MRI can be useful to predict an associated malignancy in IP, and to decide the treatment plan before intervention.
