Inverted Papilloma Research Articles

Effectiveness of the Endoscopic Prelacrimal Recess Approach for Maxillary Sinus Inverted Papilloma Removal: A Systematic Review and Meta-Analysis.

Conventional minimally invasive surgery has a high recurrence rate, and nasal morbidity can occur if the scope of surgery is expanded to complete removal of maxillary sinus inverted papilloma. To analyze the efficacy of the endoscopic prelacrimal recess approach (EPLRA) for maxillary sinus inverted papilloma removal. Eighteen studies were included in this meta-analysis. Articles comparing the prelacrimal recess approach with conventional surgery (endoscopic surgery or the Caldwell-Luc operation) for inverted papilloma removal were included. Outcomes of interest included recurrence and postoperative morbidities. The methodological quality was assessed using the Newcastle-Ottawa scale. The recurrence rates of inverted papilloma, postoperative facial or gingival numbness, and alar collapse were 3.13% (95% confidence interval [CI]: 1.32, 7.27), 9.02% (95% CI: 3.70, 20.39), and 3.39% (95% CI: 1.28, 8.68), respectively. The recurrence rate of inverted papilloma was significantly lower after the EPLRA than after conventional surgery (odds ratio [OR] = 0.2290; 95% CI: 0.0808, 0.6489). However, there were no significant differences between the procedures in the rates of facial or gingival numbness (OR = 0.4567; 95% CI: 0.1497, 1.3933), epistaxis (OR = 0.3150; 95% CI: 0.0471, 2.1044), or periorbital swelling (OR = 1.2405; 95% CI: 0.1205, 12.7731). The EPLRA can preserve the lacrimal system and is useful for maxillary sinus inverted papilloma removal due to a lower recurrence rate compared with conventional surgeries.

Technical Note: First Use of Endonasal Confocal Laser Endomicroscopy - Feasibility and Proof of Concept.

Introduction Probe-based confocal laser endomicroscopy (p-CLE) is a method for real-time in vivo visualization of mucosal changes on a cellular level. Due to the size of the endoscopes, it was mainly used in the gastrointestinal tract so far. First investigations on head and neck carcinoma described the oropharyngeal application. The further miniaturization of the laser probe now allows endonasal application and, thus, first experiences with the investigation of endonasal neoplasms. Objectives The aim of the present investigation is to elucidate, based on the morphological criteria validated in the oropharynx, whether these criteria be transferred in a similar way to the endonasal mucosa. Methods We conducted p-CLE (Cellvizio, Paris, France) with intravenous fluorescein staining in endoscopic sinus surgery in a patient with sinonasal inverted papilloma and a histologically confirmed squamous cell carcinoma. We compared the cellular visualization of pathological changes with those of healthy mucosa in the same specimen, and also with our former findings in the oropharynx. Results Endonasal p-CLE proved to be quite feasible in the surgical setting, and the transfer of malignancy criteria in analogy to histological examination could be optically retraced. Furthermore, additional criteria for tissue dignity assessment were obtained. Conclusion Our results suggest that endonasal application of p-CLE represents a valuable extension of the diagnostic repertoire available to date by an additional real-time analysis of the nasal mucosa. This is of particular value in surgically challenging anatomical areas such as the paranasal sinuses. Further investigation and validation will be necessary.

Fluorescence grid analysis for the evaluation of piecemeal surgery in sinonasal inverted papilloma: a proof-of-concept study

PurposeLocal recurrence occurs in ~ 19% of sinonasal inverted papilloma (SNIP) surgeries and is strongly associated with incomplete resection. During surgery, it is technically challenging to visualize and resect all SNIP tissue in this anatomically complex area. Proteins that are overexpressed in SNIP, such as vascular endothelial growth factor (VEGF), may serve as a target for fluorescence molecular imaging to guide surgical removal of SNIP. A proof-of-concept study was performed to investigate if the VEGF-targeted near-infrared fluorescent tracer bevacizumab-800CW specifically localizes in SNIP and whether it could be used as a clinical tool to guide SNIP surgery.MethodsIn five patients diagnosed with SNIP, 10 mg of bevacizumab-800CW was intravenously administered 3 days prior to surgery. Fluorescence molecular imaging was performed in vivo during surgery and ex vivo during the processing of the surgical specimen. Fluorescence signals were correlated with final histopathology and VEGF-A immunohistochemistry. We introduced a fluorescence grid analysis to assess the fluorescence signal in individual tissue fragments, due to the nature of the surgical procedure (i.e., piecemeal resection) allowing the detection of small SNIP residues and location of the tracer ex vivo.ResultsIn all patients, fluorescence signal was detected in vivo during endoscopic SNIP surgery. Using ex vivo fluorescence grid analysis, we were able to correlate bevacizumab-800CW fluorescence of individual tissue fragments with final histopathology. Fluorescence grid analysis showed substantial variability in mean fluorescence intensity (FImean), with SNIP tissue showing a median FImean of 77.54 (IQR 50.47–112.30) compared to 35.99 (IQR 21.48–57.81) in uninvolved tissue (p < 0.0001), although the diagnostic ability was limited with an area under the curve of 0.78.ConclusionsA fluorescence grid analysis could serve as a valid method to evaluate fluorescence molecular imaging in piecemeal surgeries. As such, although substantial differences were observed in fluorescence intensities, VEGF-A may not be the ideal target for SNIP surgery.Trial registrationNCT03925285.

HPV-Positive Status Is an Independent Factor Associated With Sinonasal Inverted Papilloma Recurrence.

The present study aimed to evaluate human papillomavirus (HPV) occurrence in sinonasal inverted papilloma (SNIP), and to assess factors associated with HPV positivity and SNIP recurrence. Prospective study. We prospectively collected clinical data and fresh tissue specimens from 90 consecutive patients treated for SNIP at Helsinki University Hospital, between 2015 and 2019. Fourteen patients with recurrent SNIP underwent repeated tumor sampling. All tissue specimens were analyzed for the presence of HPV. Factors associated with SNIP recurrence and HPV positivity were assessed. Among 107 SNIP specimens, 14 (13.1%) were positive for low-risk HPV and 6 (5.6%) were positive for high-risk HPV. HPV positivity was associated with an increased risk of recurrence (P= .004). Smoking was significantly associated with HPV positivity in SNIP (P= .01), but a history of HPV-related diseases or patient sexual habits did not correlate with HPV positivity. The recurrence rate was lower among patients with SNIP that underwent an attachment-oriented resection, compared to patients treated without attachment-oriented resections (78.6% vs 25.8%, P< .001). The risk of SNIP recurrence was highly associated with 1) HPV positivity and 2) surgery without an attachment-oriented resection. Oncogenic HPV was rare in SNIP. 3 Laryngoscope, 132:1714-1718, 2022.

NGS-based miRNome identifies miR-449 cluster as marker of malignant transformation of sinonasal inverted papilloma

Objectiveidentification of the miRNA expression profile in sinonasal inverted papilloma (SNIP) as a tool to evaluate the risk of transformation into sinonasal squamous cell carcinoma (SNSCC). Materials and Methodspaired tumour tissues and adjacent normal tissues were obtained from SNIP and SNSCC patients who had undergone surgical resection and used for next-generation sequencing (NGS)-based miRNome analysis. SNIP tissues with concomitant dysplasia (SNIP-DISP) were used as malignant transition samples. By comparing the deregulated miRNAs in SNIP and SNSCC, an miRNA cluster was identified and its physio- and clinical-pathological value was predicted. ResultsNGS identified 54 miRNAs significantly down- and upregulated in SNIP. Among them, the miR-449 cluster was upregulated in SNIP and could differentiate the benign tumour from normal tissue. Notably, the miR-449 cluster was found to be significantly underexpressed in SNSCC, and the cluster markedly changed in SNIP during the malignant transition into SNSCC. miRNA enrichment analysis and GO analysis revealed that miR-449 is involved in apoptotic and cell proliferation pathways. ConclusionsOur findings suggest that miR-449 may be involved in the molecular pathogenesis of SNIP and its malignant transformation into SNSCC. miR-449 might therefore be a useful tumour biomarker in patients with SNIP and may also have the potential to be used as a tool for detecting and monitoring the course of the possible malignant transformation.

A Systematic Review of Definitive Treatment for Inverted Papilloma Attachment Site and Associations With Recurrence.

Inverted papilloma (IP) is the most common benign neoplasm of the nasal cavity with known risk of recurrence. There is no standardized approach to definitive treatment for attachment sites. This systematic review aims to determine whether surgeon choice of technique differs by anatomic attachment site and whether different surgical techniques contribute to reduced rates of recurrence. PubMed and Ovid Medline. A systematic review was conducted for studies reporting on IP. Those that included IP recurrence rates and primary tumor attachment site were reviewed. Of 122 published studies, 14 met eligibility criteria, representing 585 patients and a recurrence rate of 5.8%. The maxillary sinus (50.9%) was the most common primary attachment site, and the sphenoid sinus was associated with the highest rate of recurrence (10.4%). The most utilized technique included debulking the tumor, removing mucosa over the attachment site, and drilling the underlying bone. The most common Krouse stage represented was T3 (53.3%). No single technique predicted a propensity for recurrence, but certain techniques are favored depending on IP attachment site. Finally, frozen sections to obtain evidence of clear margins intraoperatively significantly reduced rates of recurrence (3.4% vs 7.3%, P = .045). Based on the current literature, the most common technique to address site of attachment involves resecting mucosa and drilling the tumor base. Choice of technique appears to differ for various sites of attachment. Use of intraoperative frozen section analysis appears to be associated with decreased recurrence overall. 3.

Our Experience with Inverted Papilloma: about 61 Patients

Introduction: Inverted papilloma (IP) is the most common type of Schneiderian papilloma originating from the mucosal lining of the nose and paranasal cavities. It is a semi benign tumor with a high tendency for recurrences and malignant transformation. Management consists of a complete tumoral resection. Objective: to analyze surgical results considering the techniques (open or endoscopic surgery), the rate and time of recurrence. Method: We present herein a cohort of 61 patients treated in the CHU-UCL Godinne between 1998 and 2019. We analyzed the demographic data, the origin of the tumor, the staging, the surgical approach and the outcomes. The patients were classified into two groups: the first one includes 48 patients operated de novo in CHU-UCL Godinne and the second group 13 patients referred to us for revision surgery. Results: We observed 8 recurrences, all groups confounded. The global success rate was 87%. The number of recurrences in the first group was 6 out of 48 and 2 out of 13 in the second group. Following these results we propose an algorithm of treatment depending on the site of attachment of the IP. Conclusion: We confirmed that more extended surgeries such as Caldwell Luc procedure, medial maxillectomy, Draf IIb/III frontal sinusotomy or type III sphenoidotomy give better outcomes than more “limited” and functional surgeries such as Draf I/IIa frontal sinusotomy or middle antrostomy. The latter should be done only for specific and limited extension of the IP in the maxillary sinus. A subperiosteal dissection is mandatory in all cases. Keywords: inverted papilloma; retrospective study; surgery; recurrence

Is intraoperative margin sampling necessary in inverted papilloma resection?

To explore the association between intraoperative surgical margin sampling by the frozen sections and recurrence in inverted papilloma surgery. A multicenter, retrospective study of patients who underwent attachment-oriented IP resection in four tertiary care medical centers with a minimal follow-up of 36months. The study included 220 surgeries with a mean follow-up period of 49months (range 36-204). The endoscopic approach was used in all but 4 cases; 73% of procedures were primary. Overall recurrence was 10.45% (n = 23). Squamous cell carcinoma was found in 5 cases (2.2%). Intraoperative margin sampling was obtained in 145 cases. There was no difference in the recurrence rate between frozen section and no-frozen section groups (p = 0.44). Furthermore, margin sampling in various sites of tumor origin, in cases with concomitant nasal polyps (p = 0.53) and in revision cases (p = 0.08) showed no correlation with recurrence. In 26 cases when the surgery was extended following a positive frozen section, there was a significantly higher recurrence rate (OR = 6.94). According to our results, intraoperative margin sampling did not affect the recurrence rate of IP, and therefore, its routine use should be questioned.

Targeted gene expression profiling of inverted papilloma and squamous cell carcinoma

Inverted papilloma (IP) is a sinonasal tumor with a well-known potential for malignant transformation. The purpose of this study was to identify the genes and pathways associated with IP, with progression to carcinoma-in-situ and invasive carcinoma. To determine genes and molecular pathways that may indicate progression and correlate with histologic changes, we analyzed six IP without dysplasia, five IP with carcinoma-in-situ, and 13 squamous cell carcinoma ex-IP by targeted sequencing. The HTG EdgeSeq Oncology Biomarker Panel coupled with next-generation sequencing was used to evaluate 2560 transcripts associated with solid tumors. Progressive upregulation of 11 genes were observed (CALD1, COL1A1, COL3A1, COL4A2, COL5A2, FN1, ITGA5, LGALS1, MMP11, SERPINH1, SPARC) in the order of invasive carcinoma>carcinoma-in-situ>IP without dysplasia. When compared with IP without dysplasia, more genes are differentially expressed in invasive carcinoma than carcinoma-in-situ samples (341 downregulated/333 upregulated vs. 195 downregulated/156 upregulated). Gene set enrichment analysis determined three gene sets in common between the cohorts (epithelial mesenchymal transition, extracellular matrix organization, and coagulation). Progressive upregulation of genes specific to IP malignant degeneration has significant clinical implications. This panel of 11 genes will improve concordance of histologic classification, which can directly impact treatment and patient outcomes. Additionally, future studies on larger tumor sets may observe upregulation in the gene panel that preceded histologic changes, which may be useful for further risk stratification.

Establishment and genetic characterization of cell lines derived from proliferating nasal polyps and sinonasal inverted papillomas

To better understand the pathogenesis of nasal polyps (NPs) and sinonasal inverted papillomas (SIPs), we aimed to establish cell lines from fresh tissues of NPs and SIPs and characterize them. Primary cell cultures were obtained from two NP tissues (NP2 and NP3) and one SIP tissue (IP4). All the cells were polygonal in shape, expressed cytokeratin 14, and had normal diploid chromosome status. HPV58 DNA was detected in NP3. To obtain immortal primary cells, NP2 and IP4 cells were transduced with a combination of mutant CDK4, cyclinD1 and TERT. These cells were thereafter named NP2/K4DT and IP4/K4DT, respectively. HPV58-positive NP3 cells were transduced with TERT alone, the resulting cells named NP3/T. Phenotypic and genotypic identity of original tissues and derived cells was investigated. All the cell cultures with transgenes were confirmed to be derived from their parental cells and primary tumor tissues by analysis of short tandem repeats (STR) and maintained in vitro growth, genetic profiles and gene expression characteristics of the primary cells. These virtually immortalized cells, as well as the primary cells, have potential as in vitro models for studying the pathogenesis of NPs and SIPs and for preclinical study to develop new therapeutic agents.

A rare combination of polyp, inverted papilloma and squamous cell carcinoma of sphenoid sinus

&lt;p class="abstract"&gt;Inverted papilloma (IP) is a tumor most commonly originates from lateral wall of nose and benign in nature. Sphenoid sinus is a rare site of origin and involvement. Malignant changes are the rare possibility in the IP. In this case report we reported a rare case of squamous cell carcinoma in back ground of inverted papilloma of sphenoid sinus.&lt;/p&gt;

HPV-Associated Benign Squamous Cell Papillomas in the Upper Aero-Digestive Tract and Their Malignant Potential.

Squamous cell papilloma (SCP) in the upper aero-digestive tract is a rare disease entity with bimodal age presentation both at childhood and in adults. It originates from stratified squamous and/or respiratory epithelium. Traditionally, SCPs have been linked to chemical or mechanical irritation but, since the 1980s, they have also been associated with human papillomavirus (HPV) infection. Approximately 30% of the head and neck SCPs are associated with HPV infection, with this association being highest for laryngeal papillomas (76–94%), followed by oral (27–48%), sinonasal (25–40%), and oropharyngeal papillomas (6–7%). There is, however, a wide variation in HPV prevalence, the highest being in esophageal SCPs (11–57%). HPV6 and HPV11 are the two main HPV genotypes present, but these are also high-risk HPVs as they are infrequently detected. Some 20% of the oral and oropharyngeal papillomas also contain cutaneous HPV genotypes. Despite their benign morphology, some SCPs tend to recur and even undergo malignant transformation. The highest malignant potential is associated with sinonasal inverted papillomas (7–11%). This review discusses the evidence regarding HPV etiology of benign SCPs in the upper aero-digestive tract and their HPV-related malignant transformation. In addition, studies on HPV exposure at an early age are discussed, as are the animal models shedding light on HPV transmission, viral latency, and its reactivation.

Localization and genotyping of canine papillomavirus in canine inverted papillomas.

Numerous canine papillomaviruses (CPVs) have been identified (CPV1-23). CPV1, 2, and 6 have been associated with inverted papillomas (IPs). We retrieved 19 IPs from 3 histopathology archives, and evaluated and scored koilocytes, inclusion bodies, giant keratohyalin granules, cytoplasmic pallor, ballooning degeneration, and parakeratosis. IHC targeting major capsid proteins of PV was performed, and CPV genotyping was achieved by PCR testing. Tissue localization of CPV DNA and RNA was studied by chromogenic and RNAscope in situ hybridization (DNA-CISH, RNA-ISH, respectively). IPs were localized to the limbs (50%), trunk (30%), and head (20%), mainly as single nodules (16 of 19). In 15 of 19 cases, immunopositivity was detected within the nuclei in corneal and subcorneal epidermal layers. PCR revealed CPV1 in 11 IPs and CPV2 DNA in 3 IPs. Overall, 14 of 17 cases were positive by both DNA-CISH and RNA-ISH, in accord with PCR results. A histologic score >5 was always obtained in cases in which the viral etiology was demonstrated by IHC, DNA-CISH, and RNA-ISH. IHC and molecular approaches were useful to ascertain the viral etiology of IPs. Although IHC is the first choice for diagnostic purposes, ISH testing allows identification of PV type and the infection phase. RNA-ISH seems a promising tool to deepen our understanding of the pathogenesis of different PV types in animal species.

Nasal-type Natural Killer/T-cell Lymphoma Occurring at the Site from Which a Sinonasal Inverted Papilloma was Previously Resected: A Rare Case Report

Nasal-type Natural Killer/T-cell Lymphoma Occurring at the Site from Which a Sinonasal Inverted Papilloma was Previously Resected: A Rare Case Report

Endoscopic resection of recurrent nasal inverted papilloma

Endoscopic resection of recurrent nasal inverted papilloma

Risk factors of malignant transformation of sinonasal inverted papilloma

Objective:To explore the risk factors of malignant transformation of sinonasal inverted papilloma （SNIP）, and to improve the accuracy of preoperative diagnosis of tumor. Methods:The clinical data of 89 patients with sinonasal inverted papilloma （SNIP group, n=60） and malignant transformation of sinonasal inverted papilloma （IP-SCC, n=29） were analyzed retrospectively. Clinical symptoms, medical history, endoscopic examination, characteristic of sinonasal CT scan and MR imaging were collected and compared between two groups. Then the indicators with significant differences between the two groups were used for binary logistic regression analysis. The logistic regression model was established to predict the malignant transformation risk factors of inverted papilloma and the prediction ability of the regression model was estimated. Results:The significant differences between the two groups were: symptoms, including nasal obstruction, purulent mucus, blood in the nasal discharge; long-term smoking history; tumor attached with purulent mucus; CT scan showing bone destruction of the orbital wall and skull base; MR Imaging showing convoluted cerebriform pattern （CCP） sign, intraorbital involvement, and dural enhancement of the skull base. The results of logistic regression analysis showed that the risk factors of malignant transformation of SNIP were blood in the nasal discharge, long-term smoking history, tumor with purulent discharge, orbital wall destruction on CT scan, disappearance of CCP and orbital involvement on MRI. The accuracy rate of regression model for predicting malignant transformation of IP is 75.0%, and the accuracy rate for benign inverted papilloma is 96.7%, and the overall accuracy of the model is 89.8%. Conclusion:The risk factors for predicting malignant transformation of SNIP are blood in the nasal discharge, long-term smoking history, tumor with purulent discharge, orbital wall destruction on CT scan, and disappearance of CCP sign and orbital involvement on MRI. It's necessary to analyze all of clinical factors in order to improve the accuracy of preoperative diagnosis of sinonasal inverted papilloma.

Overexpression of Neutrophil MMP-9 and HIF-1α May Contribute to the Finger-Like Projections Formation and Histo-Pathogenesis in Nasal Inverted Papilloma.

BackgroundNasal inverted papilloma (NIP) is defined based on its histological characteristic of inverted epithelium growth into the stroma. The inversion can result in epithelial growth in the underlying connective tissue stroma when the basement membrane completely separates from the epithelial layer. To date, such inversion mechanism underlying NIP’s pathological phenomenon is unknown. Therefore, we hypothesized that mediators and soluble proteins released by neutrophils, the most predominant infiltrating cells in NIP, is vital in causing the epithelial changes and pathogenesis of NIP.MethodsWe collected 37 NIP tissues from patients who underwent surgical removal of NIP and performed hematoxylin–eosin (HE), immunohistochemical, and immunofluorescence staining to analyze in-depth the basic characteristics of NIP, including detecting the expression and distribution of MMPs and associated factors in NIP. Western blotting and quantitative real-time PCR were further performed to analyze the protein and mRNA expression levels of specific factors including MMPs, HIF-1α, and tissue inhibitors of metalloproteinases (TIMPs).ResultsWe observed finger-like projections that insert into the epithelium in NIP tissue as its main characteristics. The projections contain fibroblasts, extracellular matrix, capillaries, and infiltrating inflammatory cells. We found abundant neutrophils clustered at the finger-like projection of NIP, and also noted MMP-1 and MMP-9 were up-regulated in NIP (p<0.05), whereas TIMP-1/3 was decreased. The expression level of HIF-1α was also found to be increased in NIP tissue. We further showed that MMP-9 and HIF-1α were mainly expressed by neutrophils and were predominantly observed in the finger-like projections that contribute to the NIP pathology.ConclusionUpregulation and release of MMP-9 and HIF-1α from infiltrating neutrophils may cause damage to the epithelial basement membrane and epithelial clefts, forming finger-like projections with angiogenesis and fibroblasts insertion, resulting in epithelial growth in the tissue stroma, a typical histo-pathological characteristic in NIP.

P-132 Own experience in the treatment of patients with sinonasal inverted papilloma in Belarus

P-132 Own experience in the treatment of patients with sinonasal inverted papilloma in Belarus

Feasibility of a deep learning-based algorithm for automated detection and classification of nasal polyps and inverted papillomas on nasal endoscopic images.

Discrimination of nasal cavity mass lesions is a challenging work requiring extensive experience. A deep learning-based automated diagnostic system may help clinicians to classify nasal cavity mass lesions. We demonstrated the feasibility of a convolutional neural network (CNN)-based diagnosis system for automatic detection and classification of nasal polyps (NP) and inverted papillomas (IP). We developed a CNN-based algorithm using a transfer learning strategy and trained it on nasal endoscopic images. A total of 99 nasal endoscopic images with normal findings, 98 images with NP, and 100 images with IP were analyzed using the developed CNN. Six otolaryngologists participated in clinical visual assessment. Image-based classification performance was measured by calculating the accuracy and area under the receiver operating characteristic curve (AUC). The diagnostic performance was compared between the CNN and clinical visual assessment by human experts. The algorithm achieved an overall accuracy of 0.742 ± 0.058 with the following class accuracies: normal, 0.81± 0.14; IP, 0.57 ± 0.07; and NP, 0.83 ± 0.21. The AUC values for normal, IP, and NP were 0.91 ± 0.06, 0.82 ± 0.09, and 0.84 ± 0.06, respectively. The overall accuracy of the CNN model was comparable with the average performance of human experts (0.742vs. 0.749; p=0.11). The trained CNN model appears to reliably classify NP and IP of the nasal cavity from nasal endoscopic images; it also yields a reliable reference for diagnosing nasal cavity mass lesions during nasal endoscopy. However, further studies with more test data are warranted to improve the diagnostic accuracy of our CNN model.

Outcomes of sinonasal oncocytic papilloma by endoscopic approach in 69 patients

ObjectiveSinonasal oncocytic papilloma (SOP) is a rare subtype of sinonasal papilloma. There are currently few reports on its clinical features and outcomes after endoscopic surgical resection. This study aims to explore the clinical characteristics of SOP and potential factors predicting tumor recurrence through a single-center retrospective case series analysis. MethodsWe conducted a retrospective analysis of 69 patients who underwent endoscopic surgery of SOP from June 2012 to April 2019. The data of patients’ demographics, clinical features, follow-up period, and treatment outcomes were collected. ResultsThe series includes 43 males and 26 females with an average age of 60.2 years. The tumor commonly involved the nasal cavity (n = 59; 89.4%), followed by maxillary sinus (n = 31; 44.9%), ethmoid sinus (n = 28; 40.6%), frontal sinus (n = 6; 8.7%) and sphenoid sinus (n = 6; 8.7%). The follow-up period ranged from 3 months to 96 months (mean, 34.6 months) and nine patients (13%) developed tumor recurrence during the follow-up period. Univariate analysis found that the recurrence of SOP was significantly related to tumor attachment site, Oikawa tumor stage, and histological dysplasia (p<0.05). Multivariate COX regression analysis found that Oikawa staging system (p = 0.024) and presence of dysplasia (p = 0.04) were significantly related to tumor recurrence. ConclusionSOP had low recurrence rate which was comparable to sinonasal inverted papilloma in the endoscopic era. Our findings also demonstrated that presence of dysplasia is an independent prognostic factor for recurrence free survival.